Interview Questions
1. What is .NET Framework?
The .NET Framework has two main components: the common language runtime and the .NET Framework class library.
You can think of the runtime as an agent that manages code at execution time, providing core services such as
memory management, thread management, and remoting, while also enforcing strict type safety and other forms of
code accuracy that ensure security and robustness.
The class library, is a comprehensive, object-oriented collection of reusable types that you can use to develop
applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based
on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.
2. What is CLR?
The CLS is simply a specification that defines the rules to support language integration in such a way that programs
written in any language, yet can interoperate with one another, taking full advantage of inheritance, polymorphism,
exceptions, and other features. These rules and the specification are documented in the ECMA proposed standard
document, "Partition I Architecture", available here.
3. Is .NET a runtime service or a development platform?
Ans: It's both and actually a lot more. Microsoft .NET includes a new way of delivering software and services to
businesses and consumers. A part of Microsoft.NET is the .NET Frameworks. The .NET frameworks SDK consists of two
parts: the .NET common language runtime and the .NET class library. In addition, the SDK also includes command-line
compilers for C#, C++, JScript, and VB. You use these compilers to build applications and components. These
components require the runtime to execute so this is a development platform.
4. What are the new features of Framework 1.1 ?
1. Native Support for Developing Mobile Web Applications
2. Enable Execution of Windows Forms Assemblies Originating from the Internet
Assemblies originating from the Internet zonefor example, Microsoft Windows Forms controls embedded in an
Internet-based Web page or Windows Forms assemblies hosted on an Internet Web server and loaded either through
the Web browser or programmatically using the System.Reflection.Assembly.LoadFrom() methodnow receive
sufficient permission to execute in a semi-trusted manner. Default security policy has been changed so that assemblies
assigned by the common language runtime (CLR) to the Internet zone code group now receive the constrained
permissions associated with the Internet permission set. In the .NET Framework 1.0 Service Pack 1 and Service Pack
2, such applications received the permissions associated with the Nothing permission set and could not execute.
3. Enable Code Access Security for ASP.NET Applications
Systems administrators can now use code access security to further lock down the permissions granted to ASP.NET
Web applications and Web services. Although the operating system account under which an application runs imposes
security restrictions on the application, the code access security system of the CLR can enforce additional restrictions
on selected application resources based on policies specified by systems administrators. You can use this feature in a
shared server environment (such as an Internet service provider (ISP) hosting multiple Web applications on one
server) to isolate separate applications from one another, as well as with stand-alone servers where you want
applications to run with the minimum necessary privileges.
4. Native Support for Communicating with ODBC and Oracle Databases
5. Unified Programming Model for Smart Client Application Development
The Microsoft .NET Compact Framework brings the CLR, Windows Forms controls, and other .NET Framework features
to small devices. The .NET Compact Framework supports a large subset of the .NET Framework class library optimized
for small devices.
6. Support for IPv6
The .NET Framework 1.1 supports the emerging update to the Internet Protocol, commonly referred to as IP version 6,
or simply IPv6. This protocol is designed to significantly increase the address space used to identify communication
endpoints in the Internet to accommodate its ongoing growth.
http://msdn.microsoft.com/netframework/technologyinfo/Overview/whatsnew.aspx
5. What is Code Access Security (CAS)?
CAS is the part of the .NET security model that determines whether or not a piece of code is allowed to run, and what
resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting
your hard disk.
How does CAS work?
The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a
member of a particular code group, and each code group is granted the permissions specified in a named permission
set.
For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet'
code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet'
named permission set represents a very restrictive range of permissions.)
Who defines the CAS code groups?
Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups
defined on your system, run 'caspol -lg' from the command-line. On my ssystem it looks like this:
Level = Machine
Code Groups:
1. All code: Nothing
1.1. Zone - MyComputer: FullTrust
1.1.1. Honor SkipVerification requests: SkipVerification
1.2. Zone - Intranet: LocalIntranet
1.3. Zone - Internet: Internet
1.4. Zone - Untrusted: Nothing
1.5. Zone - Trusted: Internet
1.6. StrongName - 0024000004800000940000000602000000240000525341310004000003
000000CFCB3291AA715FE99D40D49040336F9056D7886FED46775BC7BB5430BA4444FEF8348EBD06
F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B89698D8D08AC48D69CED0FC8F83B465E08
07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272CEEEE72F1660B71927D38561AABF5C
AC1DF1734633C602F8F2D5: Everything
Note the hierarchy of code groups - the top of the hierarchy is the most general ('All code'), which is then sub-divided
into several groups, each of which in turn can be sub-divided. Also note that (somewhat counter-intuitively) a sub-
group can be associated with a more permissive permission set than its parent.
How do I define my own code group?
Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your
system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new
code group as a sub-group of the 'Zone - Internet' group, like this:
caspol -ag 1.3 -site www.mydomain.com FullTrust
Now if you run caspol -lg you will see that the new group has been added as group 1.3.1:
...
1.3. Zone - Internet: Internet
1.3.1. Site - www.mydomain.com: FullTrust
...
Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the
command-line. The underlying runtime never sees it.
How do I change the permission set for a code group?
Use caspol. If you are the machine administrator, you can operate at the 'machine' level - which means not only that
the changes you make become the default for the machine, but also that users cannot change the permissions to be
more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them
more restrictive. For example, to allow intranet code to do what it likes you might do this:
caspol -cg 1.2 FullTrust
Note that because this is more permissive than the default policy (on a standard system), you should only do this at
the machine level - doing it at the user level will have no effect.
Can I create my own permission set?
Yes. Use caspol -ap, specifying an XML file containing the permissions in the permission set. To save you some time,
here is a sample file corresponding to the 'Everything' permission set - just edit to suit your needs. When you have
edited the sample, add it to the range of available permission sets like this:
caspol -ap samplepermset.xml
Then, to apply the permission set to a code group, do something like this:
caspol -cg 1.3 SamplePermSet (By default, 1.3 is the 'Internet' code group)
I'm having some trouble with CAS. How can I diagnose my problem?
Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly
belongs to, using caspol -rsg. Similarly, you can ask what permissions are being applied to a particular assembly using
caspol -rsp.
I can't be bothered with all this CAS stuff. Can I turn it off?
Yes, as long as you are an administrator. Just run: caspol -s off
6. What is MSIL, IL?
When compiling to managed code, the compiler translates your source code into Microsoft intermediate language
(MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes
instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and
logical operations, control flow, direct memory access, exception handling, and other operations. Microsoft
intermediate language (MSIL) is a language used as the output of a number of compilers and as the input to a just-in-
time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.
7. Can I write IL programs directly?
Yes. Peter Drayton posted this simple example to the DOTNET mailing list:
.assembly MyAssembly {}
.class MyApp {
.method static void Main() {
.entrypoint
ldstr "Hello, IL!"
call void System.Console::WriteLine(class System.Object)
ret
}
}
Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be generated.
Can I do things in IL that I can't do in C#?
Yes. A couple of simple examples are that you can throw exceptions that are not derived from System.Exception, and
you can have non-zero-based arrays.
8. What is CTS?
The common type system defines how types are declared, used, and managed in the runtime, and is also an important
part of the runtime's support for cross-language integration.
The common type system supports two general categories of types, each of which is further divided into
subcategories:
Value types
Value types directly contain their data, and instances of value types are either allocated on the stack or allocated inline
in a structure. Value types can be built-in (implemented by the runtime), user-defined, or enumerations.
Reference types
Reference types store a reference to the value's memory address, and are allocated on the heap. Reference types can
be self-describing types, pointer types, or interface types. The type of a reference type can be determined from values
of self-describing types. Self-describing types are further split into arrays and class types. The class types are user-
defined classes, boxed value types, and delegates.
9. What is JIT (just in time)? how it works?
Before Microsoft intermediate language (MSIL) can be executed, it must be converted by a .NET Framework just-in-
time (JIT) compiler to native code, which is CPU-specific code that runs on the same computer architecture as the JIT
compiler.
Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it
converts the MSIL as it is needed during execution and stores the resulting native code so that it is accessible for
subsequent calls.
The runtime supplies another mode of compilation called install-time code generation. The install-time code generation
mode converts MSIL to native code just as the regular JIT compiler does, but it converts larger units of code at a time,
storing the resulting native code for use when the assembly is subsequently loaded and executed.
As part of compiling MSIL to native code, code must pass a verification process unless an administrator has established
a security policy that allows code to bypass verification. Verification examines MSIL and metadata to find out whether
the code can be determined to be type safe, which means that it is known to access only the memory locations it is
authorized to access.
10. What is strong name?
A name that consists of an assembly's identityits simple text name, version number, and culture information (if
provided)strengthened by a public key and a digital signature generated over the assembly.
11. What is portable executable (PE)?
The file format defining the structure that all executable files (EXE) and Dynamic Link Libraries (DLL) must use to allow
them to be loaded and executed by Windows. PE is derived from the Microsoft Common Object File Format (COFF).
The EXE and DLL files created using the .NET Framework obey the PE/COFF formats and also add additional header
and data sections to the files that are only used by the CLR. The specification for the PE/COFF file formats is available
at http://www.microsoft.com/whdc/hwdev/hardware/pecoffdown.mspx
12. Which namespace is the base class for .net Class library?
Ans: system.object
13. What is Event - Delegate? clear syntax for writing a event delegate
The event keyword lets you specify a delegate that will be called upon the occurrence of some "event" in your code.
The delegate can have one or more associated methods that will be called when your code indicates that the event has
occurred. An event in one program can be made available to other programs that target the .NET Framework Common
Language Runtime.
// keyword_delegate.cs
// delegate declaration
delegate void MyDelegate(int i);
class Program
{
public static void Main()
{
TakesADelegate(new MyDelegate(DelegateFunction));
}
public static void TakesADelegate(MyDelegate SomeFunction)
{
SomeFunction(21);
}
public static void DelegateFunction(int i)
{
System.Console.WriteLine("Called by delegate with number: {0}.", i);
}
}
14. What are object pooling and connection pooling and difference? Where do we set the Min and Max
Pool size for connection pooling?
Object pooling is a COM+ service that enables you to reduce the overhead of creating each object from scratch. When
an object is activated, it is pulled from the pool. When the object is deactivated, it is placed back into the pool to await
the next request. You can configure object pooling by applying the ObjectPoolingAttribute attribute to a class that
derives from the System.EnterpriseServices.ServicedComponent class.
Object pooling lets you control the number of connections you use, as opposed to connection pooling, where you
control the maximum number reached.
Following are important differences between object pooling and connection pooling:
Creation. When using connection pooling, creation is on the same thread, so if there is nothing in the pool, a
connection is created on your behalf. With object pooling, the pool might decide to create a new object. However, if
you have already reached your maximum, it instead gives you the next available object. This is crucial behavior when
it takes a long time to create an object, but you do not use it for very long.
Enforcement of minimums and maximums. This is not done in connection pooling. The maximum value in
object pooling is very important when trying to scale your application. You might need to multiplex thousands of
requests to just a few objects. (TPC/C benchmarks rely on this.)
COM+ object pooling is identical to what is used in .NET Framework managed SQL Client connection pooling. For
example, creation is on a different thread and minimums and maximums are enforced.
15. What is Application Domain?
The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide
isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn't scale well. The
.NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain
is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory.
Objects in different application domains communicate either by transporting copies of objects across application
domain boundaries, or by using a proxy to exchange messages.
MarshalByRefObject is the base class for objects that communicate across application domain boundaries by
exchanging messages using a proxy. Objects that do not inherit from MarshalByRefObject are implicitly marshal by
value. When a remote application references a marshal by value object, a copy of the object is passed across
application domain boundaries.
How does an AppDomain get created?
AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a
.NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every
application.
AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain,
creates an instance of an object inside it, and then executes one of the object's methods. Note that you must name
the executable 'appdomaintest.exe' for this code to work as-is.
using System;
using System.Runtime.Remoting;
public class CAppDomainInfo : MarshalByRefObject
{
public string GetAppDomainInfo()
{
return "AppDomain = " + AppDomain.CurrentDomain.FriendlyName;
}
}
public class App
{
public static int Main()
{
AppDomain ad = AppDomain.CreateDomain( "Andy's new domain", null, null );
ObjectHandle oh = ad.CreateInstance( "appdomaintest", "CAppDomainInfo" );
CAppDomainInfo adInfo = (CAppDomainInfo)(oh.Unwrap());
string info = adInfo.GetAppDomainInfo();
Console.WriteLine( "AppDomain info: " + info );
return 0;
}
}
16. What is serialization in .NET? What are the ways to control serialization?
Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of
creating an object from a stream of bytes. Serialization/Deserialization is mostly used to transport objects (e.g. during
remoting), or to persist objects (e.g. to a file or database).Serialization can be defined as the process of storing the
state of an object to a storage medium. During this process, the public and private fields of the object and the name of
the class, including the assembly containing the class, are converted to a stream of bytes, which is then written to a
data stream. When the object is subsequently deserialized, an exact clone of the original object is created.
Binary serialization preserves type fidelity, which is useful for preserving the state of an object between
different invocations of an application. For example, you can share an object between different applications by
serializing it to the clipboard. You can serialize an object to a stream, disk, memory, over the network, and so forth.
Remoting uses serialization to pass objects "by value" from one computer or application domain to another.
XML serialization serializes only public properties and fields and does not preserve type fidelity. This is useful
when you want to provide or consume data without restricting the application that uses the data. Because XML is an
open standard, it is an attractive choice for sharing data across the Web. SOAP is an open standard, which makes it an
attractive choice.
There are two separate mechanisms provided by the .NET class library - XmlSerializer and
SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses
SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.
Why do I get errors when I try to serialize a Hashtable?
XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter
and BinaryFormatter do not have this restriction.
17. What is the use of trace utility?
**
18. What are server controls?
ASP.NET server controls are components that run on the server and encapsulate user-interface and other related
functionality. They are used in ASP.NET pages and in ASP.NET code-behind classes.
19. What is the difference between Web User Control and Web Custom Control?
Custom Controls
Web custom controls are compiled components that run on the server and that encapsulate user-interface and other
related functionality into reusable packages. They can include all the design-time features of standard ASP.NET server
controls, including full support for Visual Studio design features such as the Properties window, the visual designer,
and the Toolbox.
There are several ways that you can create Web custom controls:
You can compile a control that combines the functionality of two or more existing controls. For example, if you
need a control that encapsulates a button and a text box, you can create it by compiling the existing controls together.
If an existing server control almost meets your requirements but lacks some required features, you can
customize the control by deriving from it and overriding its properties, methods, and events.
If none of the existing Web server controls (or their combinations) meet your requirements, you can create a
custom control by deriving from one of the base control classes. These classes provide all the basic functionality of
Web server controls, so you can focus on programming the features you need.
If none of the existing ASP.NET server controls meet the specific requirements of your applications, you can create
either a Web user control or a Web custom control that encapsulates the functionality you need. The main difference
between the two controls lies in ease of creation vs. ease of use at design time.
Web user controls are easy to make, but they can be less convenient to use in advanced scenarios. You develop Web
user controls almost exactly the same way that you develop Web Forms pages. Like Web Forms, user controls can be
created in the visual designer, they can be written with code separated from the HTML, and they can handle execution
events. However, because Web user controls are compiled dynamically at run time they cannot be added to the
Toolbox, and they are represented by a simple placeholder glyph when added to a page. This makes Web user controls
harder to use if you are accustomed to full Visual Studio .NET design-time support, including the Properties window
and Design view previews. Also, the only way to share the user control between applications is to put a separate copy
in each application, which takes more maintenance if you make changes to the control.
Web custom controls are compiled code, which makes them easier to use but more difficult to create; Web custom
controls must be authored in code. Once you have created the control, however, you can add it to the Toolbox and
display it in a visual designer with full Properties window support and all the other design-time features of ASP.NET
server controls. In addition, you can install a single copy of the Web custom control in the global assembly cache and
share it between applications, which makes maintenance easier.
Web user controls Web custom controls
Easier to create Harder to create
Limited support for consumers who use a visual design tool Full visual design tool support for consumers
A separate copy of the control is required in each application Only a single copy of the control is required, in the
global assembly cache
Cannot be added to the Toolbox in Visual Studio Can be added to the Toolbox in Visual Studio
Good for static layout Good for dynamic layout
20. What is exception handling?
When an exception occurs, the system searches for the nearest catch clause that can handle the exception, as
determined by the run-time type of the exception. First, the current method is searched for a lexically enclosing try
statement, and the associated catch clauses of the try statement are considered in order. If that fails, the method that
called the current method is searched for a lexically enclosing try statement that encloses the point of the call to the
current method. This search continues until a catch clause is found that can handle the current exception, by naming
an exception class that is of the same class, or a base class, of the run-time type of the exception being thrown. A
catch clause that doesn't name an exception class can handle any exception.
Once a matching catch clause is found, the system prepares to transfer control to the first statement of the catch
clause. Before execution of the catch clause begins, the system first executes, in order, any finally clauses that were
associated with try statements more nested that than the one that caught the exception.
Exceptions that occur during destructor execution are worth special mention. If an exception occurs during destructor
execution, and that exception is not caught, then the execution of that destructor is terminated and the destructor of
the base class (if any) is called. If there is no base class (as in the case of the object type) or if there is no base class
destructor, then the exception is discarded.
21. What is Assembly?
Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment,
version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources
that are built to work together and form a logical unit of functionality. An assembly provides the common language
runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist
outside the context of an assembly.
Assemblies are a fundamental part of programming with the .NET Framework. An assembly performs the following
functions:
It contains code that the common language runtime executes. Microsoft intermediate language (MSIL) code in
a portable executable (PE) file will not be executed if it does not have an associated assembly manifest. Note that each
assembly can have only one entry point (that is, DllMain, WinMain, or Main).
It forms a security boundary. An assembly is the unit at which permissions are requested and granted.
It forms a type boundary. Every type's identity includes the name of the assembly in which it resides. A type
called MyType loaded in the scope of one assembly is not the same as a type called MyType loaded in the scope of
another assembly.
It forms a reference scope boundary. The assembly's manifest contains assembly metadata that is used for
resolving types and satisfying resource requests. It specifies the types and resources that are exposed outside the
assembly. The manifest also enumerates other assemblies on which it depends.
It forms a version boundary. The assembly is the smallest versionable unit in the common language runtime;
all types and resources in the same assembly are versioned as a unit. The assembly's manifest describes the version
dependencies you specify for any dependent assemblies.
It forms a deployment unit. When an application starts, only the assemblies that the application initially calls
must be present. Other assemblies, such as localization resources or assemblies containing utility classes, can be
retrieved on demand. This allows applications to be kept simple and thin when first downloaded.
It is the unit at which side-by-side execution is supported.
Assemblies can be static or dynamic. Static assemblies can include .NET Framework types (interfaces and classes), as
well as resources for the assembly (bitmaps, JPEG files, resource files, and so on). Static assemblies are stored on disk
in PE files. You can also use the .NET Framework to create dynamic assemblies, which are run directly from memory
and are not saved to disk before execution. You can save dynamic assemblies to disk after they have executed.
There are several ways to create assemblies. You can use development tools, such as Visual Studio .NET, that you
have used in the past to create .dll or .exe files. You can use tools provided in the .NET Framework SDK to create
assemblies with modules created in other development environments. You can also use common language runtime
APIs, such as Reflection.Emit, to create dynamic assemblies.
22. What are the contents of assembly?
In general, a static assembly can consist of four elements:
The assembly manifest, which contains assembly metadata.
Type metadata.
Microsoft intermediate language (MSIL) code that implements the types.
A set of resources.
23. What are the different types of assemblies?
Private, Public/Shared, Satellite
24. What is the difference between a private assembly and a shared assembly?
0. Location and visibility: A private assembly is normally used by a single application, and is stored in the
application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache,
which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code
which many applications will find useful, e.g. the .NET framework classes.
1. Versioning: The runtime enforces versioning constraints only on shared assemblies, not on private assemblies.
25. What are Satellite Assemblies? How you will create this? How will you get the different language
strings?
Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific
assemblies work in side-by-side execution because the application has a separate product ID for each language and
installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application
removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET
Framework files are removed unless the last language for that .NET Framework version is being removed.
(For example, English and Japanese editions of the .NET Framework version 1.1 share the same core files. The
Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources in a \ja subdirectory. An
application that supports the .NET Framework version 1.1, regardless of its language, always uses the same core
runtime files.)
http://www.ondotnet.com/lpt/a/2637
**
26. How will u load dynamic assembly? How will create assemblies at run time?
**
27. What is Assembly manifest? what all details the assembly manifest will contain?
Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the
assembly relate to each other. The assembly manifest contains this assembly metadata. An assembly manifest
contains all the metadata needed to specify the assembly's version requirements and security identity, and all
metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly
manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a
standalone PE file that contains only assembly manifest information.
It contains Assembly name, Version number, Culture, Strong name information, List of all files in the assembly, Type
reference information, Information on referenced assemblies.
28. Difference between assembly manifest & metadata?
assembly manifest - An integral part of every assembly that renders the assembly self-describing. The assembly
manifest contains the assembly's metadata. The manifest establishes the assembly identity, specifies the files that
make up the assembly implementation, specifies the types and resources that make up the assembly, itemizes the
compile-time dependencies on other assemblies, and specifies the set of permissions required for the assembly to run
properly. This information is used at run time to resolve references, enforce version binding policy, and validate the
integrity of loaded assemblies. The self-describing nature of assemblies also helps makes zero-impact install and
XCOPY deployment feasible.
metadata - Information that describes every element managed by the common language runtime: an assembly,
loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as
well as security attributes, marshaling data, extended class and member definitions, version binding, and other
information required by the runtime.
29. What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to
public? Steps) How more than one version of an assembly can keep in same place?
Each computer where the common language runtime is installed has a machine-wide code cache called the global
assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several
applications on the computer. You should share assemblies by installing them into the global assembly cache only
when you need to.
Steps
- Create a strong name using sn.exe tool
eg: sn -k keyPair.snk
- with in AssemblyInfo.cs add the generated file name
eg: [assembly: AssemblyKeyFile("abc.snk")]
- recompile project, then install it to GAC by either
drag & drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly) (shfusion.dll tool)
or
gacutil -i abc.dll
30. If I have more than one version of one assemblies, then how'll I use old version (how/where to specify version
number?)in my application?
**
31. How to find methods of a assembly file (not using ILDASM)
Reflection
32. What is Garbage Collection in .Net? Garbage collection process?
The process of transitively tracing through all pointers to actively used objects in order to locate all objects that can be
referenced, and then arranging to reuse any heap memory that was not found during this trace. The common language
runtime garbage collector also compacts the memory that is in use to reduce the working space needed for the heap.
33. Readonly vs. const?
A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the
declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used.
Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants, as in the
following example:
public static readonly uint l1 = (uint) DateTime.Now.Ticks;
34. What is Reflection in .NET? Namespace? How will you load an assembly which is not referenced by
current assembly?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged
along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism
called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a
module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in
COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across
context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types
dynamically at run-time (see System.Reflection.Emit.TypeBuilder).
35. What is Custom attribute? How to create? If I'm having custom attribute in an assembly, how to
say that name in the code?
A: The primary steps to properly design custom attribute classes are as follows:
. Applying the AttributeUsageAttribute ([AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple =
true)])
a. Declaring the attribute. (class public class MyAttribute : System.Attribute { // . . . })
b. Declaring constructors (public MyAttribute(bool myvalue) { this.myvalue = myvalue; })
c. Declaring properties
d. public bool MyProperty
e. {
f. get {return this.myvalue;}
g. set {this.myvalue = value;}
h. }
36. The following example demonstrates the basic way of using reflection to get access to custom
attributes.
class MainClass
{
public static void Main()
{
System.Reflection.MemberInfo info = typeof(MyClass);
object[] attributes = info.GetCustomAttributes();
for (int i = 0; i < attributes.Length; i ++)
{
System.Console.WriteLine(attributes[i]);
}
}
}
37. What is the managed and unmanaged code in .net?
The .NET Framework provides a run-time environment called the Common Language Runtime, which manages the
execution of code and provides services that make the development process easier. Compilers and tools expose the
runtime's functionality and enable you to write code that benefits from this managed execution environment. Code that
you develop with a language compiler that targets the runtime is called managed code; it benefits from features such
as cross-language integration, cross-language exception handling, enhanced security, versioning and deployment
support, a simplified model for component interaction, and debugging and profiling services.
38. How do you create threading in .NET? What is the namespace for that?
System.Threading.Thread
39. Serialize and MarshalByRef?
40. using directive vs using statement
You create an instance in a using statement to ensure that Dispose is called on the object when the using statement is
exited. A using statement can be exited either when the end of the using statement is reached or if, for example, an
exception is thrown and control leaves the statement block before the end of the statement.
The using directive has two uses:
Create an alias for a namespace (a using alias).
Permit the use of types in a namespace, such that, you do not have to qualify the use of a type in that
namespace (a using directive).
41. Describe the Managed Execution Process?
The managed execution process includes the following steps:
0. Choosing a compiler.
To obtain the benefits provided by the common language runtime, you must use one or more language compilers that
target the runtime.
1. Compiling your code to Microsoft intermediate language (MSIL).
Compiling translates your source code into MSIL and generates the required metadata.
2. Compiling MSIL to native code.
At execution time, a just-in-time (JIT) compiler translates the MSIL into native code. During this compilation, code
must pass a verification process that examines the MSIL and metadata to find out whether the code can be determined
to be type safe.
3. Executing your code.
The common language runtime provides the infrastructure that enables execution to take place as well as a variety of
services that can be used during execution.
42. What is Active Directory? What is the namespace used to access the Microsoft Active Directories?
What are ADSI Directories?
Active Directory Service Interfaces (ADSI) is a programmatic interface for Microsoft Windows Active Directory. It
enables your applications to interact with diverse directories on a network, using a single interface. Visual Studio .NET
and the .NET Framework make it easy to add ADSI functionality with the DirectoryEntry and DirectorySearcher
components.
Using ADSI, you can create applications that perform common administrative tasks, such as backing up databases,
accessing printers, and administering user accounts. ADSI makes it possible for you to:
Log on once to work with diverse directories. The DirectoryEntry component class provides username and
password properties that can be entered at runtime and communicated to the Active Directory object you are binding
to.
Use a single application programming interface (API) to perform tasks on multiple directory systems by
offering the user a variety of protocols to use. The DirectoryServices namespace provides the classes to perform most
administrative functions.
Perform "rich querying" on directory systems. ADSI technology allows for searching for an object by specifying
two query dialects: SQL and LDAP.
Access and use a single, hierarchical structure for administering and maintaining diverse and complicated
network configurations by accessing an Active Directory tree.
Integrate directory information with databases such as SQL Server. The DirectoryEntry path may be used as
an ADO.NET connection string provided that it is using the LDAP provider.
using System.DirectoryServices;
43. How Garbage Collector (GC) Works?
The methods in this class influence when an object is garbage collected and when resources allocated by an object are
released. Properties in this class provide information about the total amount of memory available in the system and
the age category, or generation, of memory allocated to an object. Periodically, the garbage collector performs
garbage collection to reclaim memory allocated to objects for which there are no valid references. Garbage collection
happens automatically when a request for memory cannot be satisfied using available free memory. Alternatively, an
application can force garbage collection using the Collect method.
Garbage collection consists of the following steps:
0. The garbage collector searches for managed objects that are referenced in managed code.
1. The garbage collector attempts to finalize objects that are not referenced.
2. The garbage collector frees objects that are not referenced and reclaims their memory.
44. Why do we need to call CG.SupressFinalize?
Requests that the system not call the finalizer method for the specified object.
public static void SuppressFinalize(
object obj
); The method removes obj from the set of objects that require finalization. The obj parameter is required to be the
caller of this method.
Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent
the garbage collector from calling Object.Finalize on an object that does not require it.
45. What is nmake tool?
The Nmake tool (Nmake.exe) is a 32-bit tool that you use to build projects based on commands contained in a .mak
file.
usage : nmake -a all
46. What are Namespaces?
The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way
to create globally-unique types. Even if you do not explicitly declare one, a default namespace is created. This
unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global
namespace is available for use in a named namespace. Namespaces implicitly have public access and this is not
modifiable.
47. C++ & C# differences
**
48. If you want to write your own dot net language, what steps you will u take care?
49. What is custom events? How to create it?
50. how dot net compiled code will become platform independent?
51. without modifying source code if we compile again, will it be generated MSIL again?
52. Describe the difference between inline and code behind - which is best in a loosely coupled solution?
53. What is the difference between CONST and READONLY?
54. What is the difference between ref & out parameters?
What is the difference between arrays and Arraylist?
55. What are indexers?
56. How to create events for a control?
57. Explain about SOAP
58. Practical Example of Passing an Events to delegates
59. How can you read 3rd line from a text file?
60. What is Asynchronous call and how it can be implemented using delegates?
61. What is the difference between Array and LinkedList?
62. What is Jagged Arrays?
A jagged array is an array whose elements are arrays. The elements of a jagged array can be of different dimensions
and sizes. A jagged array is sometimes called an "array-of-arrays."
COM
63. Interop Services?
The common language runtime provides two mechanisms for interoperating with unmanaged code:
Platform invoke, which enables managed code to call functions exported from an unmanaged library.
COM interop, which enables managed code to interact with COM objects through interfaces.
Both platform invoke and COM interop use interop marshaling to accurately move method arguments between caller
and callee and back, if required.
64. How does u handle this COM components developed in other programming languages in .NET?
65. What is RCW (Runtime Callable Wrappers)?
The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW).
Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a
.NET client and a COM object.
66. What is CCW (COM Callable Wrapper)
A proxy object generated by the common language runtime so that existing COM applications can use managed
classes, including .NET Framework classes, transparently.
67. How CCW and RCW is working?
**
68. How will you register com+ services?
The .NET Framework SDK provides the .NET Framework Services Installation Tool (Regsvcs.exe - a command-line tool)
to manually register an assembly containing serviced components. You can also access these registration features
programmatically with the System.EnterpriseServicesRegistrationHelper class by creating an instance of class
RegistrationHelper and using the method InstallAssembly
69. What is use of ContextUtil class?
ContextUtil is the preferred class to use for obtaining COM+ context information.
70. What is the new three features of COM+ services, which are not there in COM (MTS)?
**
71. Is the COM architecture same as .Net architecture? What is the difference between them?
**
72. Can we copy a COM dll to GAC folder?
**
73. What is Pinvoke?
Platform invoke is a service that enables managed code to call unmanaged functions implemented in dynamic-link
libraries (DLLs), such as those in the Win32 API. It locates and invokes an exported function and marshals its
arguments (integers, strings, arrays, structures, and so on) across the interoperation boundary as needed.
74. Is it true that COM objects no longer need to be registered on the server?
Answer: Yes and No. Legacy COM objects still need to be registered on the server before they can be used. COM
developed using the new .NET Framework will not need to be registered. Developers will be able to auto-register these
objects just by placing them in the 'bin' folder of the application.
75. Can .NET Framework components use the features of Component Services?
Answer: Yes, you can use the features and functions of Component Services from a .NET Framework component.
http://msdn.microsoft.com/library/techart/Pahlcompserv.htm
OOPS
76. What are the OOPS concepts?
1) Encapsulation: It is the mechanism that binds together code and data in manipulates, and keeps both safe from outside interference and misuse. In short it isolates a particular code and data from all other codes and data. A well-
defined interface controls the access to that particular code and data.
2) Inheritance: It is the process by which one object acquires the properties of another object. This supports the hierarchical classification. Without the use of hierarchies, each object would need to define all its characteristics explicitly. However, by use of inheritance, an object need only define those qualities that make it unique within its class. It can inherit its general attributes from its parent. A new sub-class inherits all of the attributes of all of its ancestors.
3) Polymorphism: It is a feature that allows one interface to be used for general class of actions. The specific action is determined by the exact nature of the situation. In general polymorphism means "one interface, multiple methods", This means that it is possible to design a generic interface to a group of related activities. This helps reduce complexity by allowing the same interface to be used to specify a general class of action. It is the compiler's job to select the specific action (that is, method) as it applies to each situation.
77. What is the difference between a Struct and a Class?
The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it
is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an
array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is
less expensive.
When you create a struct object using the new operator, it gets created and the appropriate constructor is
called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will
remain unassigned and the object cannot be used until all of the fields are initialized.
It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always
provided to initialize the struct members to their default values.
It is an error to initialize an instance field in a struct.
There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class,
and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement
interfaces, and it does that exactly as classes do.
A struct is a value type, while a class is a reference type.
78. Value type & reference types difference? Example from .NET. Integer & struct are value types or
reference types in .NET?
Most programming languages provide built-in data types, such as integers and floating-point numbers, that are copied
when they are passed as arguments (that is, they are passed by value). In the .NET Framework, these are called value
types. The runtime supports two kinds of value types:
Built-in value types
The .NET Framework defines built-in value types, such as System.Int32 and System.Boolean, which correspond and
are identical to primitive data types used by programming languages.
User-defined value types
Your language will provide ways to define your own value types, which derive from System.ValueType. If you want to
define a type representing a value that is small, such as a complex number (using two floating-point numbers), you
might choose to define it as a value type because you can pass the value type efficiently by value. If the type you are
defining would be more efficiently passed by reference, you should define it as a class instead.
Variables of reference types, referred to as objects, store references to the actual data. This following are the
reference types:
class
interface
delegate
This following are the built-in reference types:
object
string
79. What is Inheritance, Multiple Inheritance, Shared and Repeatable Inheritance?
**
80. What is Method overloading?
Method overloading occurs when a class contains two methods with the same name, but different signatures.
81. What is Method Overriding? How to override a function in C#?
Use the override modifier to modify a method, a property, an indexer, or an event. An override method provides a new
implementation of a member inherited from a base class. The method overridden by an override declaration is known
as the overridden base method. The overridden base method must have the same signature as the override method.
You cannot override a non-virtual or static method. The overridden base method must be virtual, abstract, or override.
82. Can we call a base class method without creating instance?
Its possible If its a static method.
Its possible by inheriting from that class also.
Its possible from derived classes using base keyword.
83. You have one base class virtual function how will call that function from derived class?
Ans:
class a
{
public virtual int m()
{
return 1;
}
}
class b:a
{
public int j()
{
return m();
}
}
84. In which cases you use override and new base?
Use the new modifier to explicitly hide a member inherited from a base class. To hide an inherited member, declare it
in the derived class using the same name, and modify it with the new modifier.
C# Language features
85. What are Sealed Classes in C#?
The sealed modifier is used to prevent derivation from a class. A compile-time error occurs if a sealed class is specified
as the base class of another class. (A sealed class cannot also be an abstract class)
86. What is Polymorphism? How does VB.NET/C# achieve polymorphism?
**
class Token
{
public string Display()
{
//Implementation goes here
return "base";
}
}
class IdentifierToken:Token
{
public new string Display() //What is the use of new keyword
{
//Implementation goes here
return "derive";
}
}
static void Method(Token t)
{
Console.Write(t.Display());
}
public static void Main()
{
IdentifierToken Variable=new IdentifierToken();
Method(Variable); //Which Class Method is called here
Console.ReadLine();
}
For the above code What is the "new" keyword and Which Class Method is
called here
A: it will call base class Display method
class Token
{
public virtual string Display()
{
//Implementation goes here
return "base";
}
}
class IdentifierToken:Token
{
public override string Display() //What is the use of new keyword
{
//Implementation goes here
return "derive";
}
}
static void Method(Token t)
{
Console.Write(t.Display());
}
public static void Main()
{
IdentifierToken Variable=new IdentifierToken();
Method(Variable); //Which Class Method is called here
Console.ReadLine();
}
A: Derive
87. In which Scenario you will go for Interface or Abstract Class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide
implementation. They are implemented by classes, and defined as separate entities from classes. Even though class
inheritance allows your classes to inherit implementation from a base class, it also forces you to make most of your
design decisions when the class is first published.
Abstract classes are useful when creating components because they allow you specify an invariant level of functionality
in some methods, but leave the implementation of other methods until a specific implementation of that class is
needed. They also version well, because if additional functionality is needed in derived classes, it can be added to the
base class without breaking code.
Interfaces vs. Abstract Classes
Feature Interface Abstract class
Multiple inheritance A class may implement several interfaces. A class may extend only one abstract class.
Default implementation An interface cannot provide any code at all, much less default code. An abstract class
can provide complete code, default code, and/or just stubs that have to be overridden.
Constants Static final constants only, can use them without qualification in classes that implement the interface.
On the other paw, these unqualified names pollute the namespace. You can use them and it is not obvious where they
are coming from since the qualification is optional. Both instance and static constants are possible. Both static
and instance intialiser code are also possible to compute the constants.
Third party convenience An interface implementation may be added to any existing third party class. A third
party class must be rewritten to extend only from the abstract class.
is-a vs -able or can-do Interfaces are often used to describe the peripheral abilities of a class, not its central identity,
e.g. an Automobile class might implement the Recyclable interface, which could apply to many otherwise totally
unrelated objects. An abstract class defines the core identity of its descendants. If you defined a Dog abstract
class then Damamation descendants are Dogs, they are not merely dogable. Implemented interfaces enumerate the
general things a class can do, not the things a class is.
Plug-in You can write a new replacement module for an interface that contains not one stick of code in common with
the existing implementations. When you implement the interface, you start from scratch without any default
implementation. You have to obtain your tools from other classes; nothing comes with the interface other than a few
constants. This gives you freedom to implement a radically different internal design. You must use the abstract
class as-is for the code base, with all its attendant baggage, good or bad. The abstract class author has imposed
structure on you. Depending on the cleverness of the author of the abstract class, this may be good or bad. Another
issue that's important is what I call "heterogeneous vs. homogeneous." If implementors/subclasses are homogeneous,
tend towards an abstract base class. If they are heterogeneous, use an interface. (Now all I have to do is come up with
a good definition of hetero/homogeneous in this context.) If the various objects are all of-a-kind, and share a common
state and behavior, then tend towards a common base class. If all they share is a set of method signatures, then tend
towards an interface.
Homogeneity If all the various implementations share is the method signatures, then an interface works best. If
the various implementations are all of a kind and share a common status and behavior, usually an abstract class works
best.
Maintenance If your client code talks only in terms of an interface, you can easily change the concrete
implementation behind it, using a factory method. Just like an interface, if your client code talks only in terms
of an abstract class, you can easily change the concrete implementation behind it, using a factory method.
Speed Slow, requires extra indirection to find the corresponding method in the actual class. Modern JVMs are
discovering ways to reduce this speed penalty. Fast
Terseness The constant declarations in an interface are all presumed public static final, so you may leave that
part out. You can't call any methods to compute the initial values of your constants. You need not declare individual
methods of an interface abstract. They are all presumed so. You can put shared code into an abstract class,
where you cannot into an interface. If interfaces want to share code, you will have to write other bubblegum to
arrange that. You may use methods to compute the initial values of your constants and variables, both instance and
static. You must declare all the individual methods of an abstract class abstract.
Adding functionality If you add a new method to an interface, you must track down all implementations of that
interface in the universe and provide them with a concrete implementation of that method. If you add a new method
to an abstract class, you have the option of providing a default implementation of it. Then all existing code will
continue to work without change.
see the code
interface ICommon
{
int getCommon();
}
interface ICommonImplements1:ICommon
{
}
interface ICommonImplements2:ICommon
{
}
public class a:ICommonImplements1,ICommonImplements2
{
}
How to implement getCommon method in class a? Are you seeing any problem in the implementation?
Ans:
public class a:ICommonImplements1,ICommonImplements2
{
public int getCommon()
{
return 1;
}
}
interface IWeather
{
void display();
}
public class A:IWeather
{
public void display()
{
MessageBox.Show("A");
}
}
public class B:A
{
}
public class C:B,IWeather
{
public void display()
{
MessageBox.Show("C");
}
}
When I instantiate C.display(), will it work?
interface IPrint
{
string Display();
}
interface IWrite
{
string Display();
}
class PrintDoc:IPrint,IWrite
{
//Here is implementation
}
how to implement the Display in the class printDoc (How to resolve the naming Conflict) A: no naming conflicts
class PrintDoc:IPrint,IWrite
{
public string Display()
{
return "s";
}
}
interface IList
{
int Count { get; set; }
}
interface ICounter
{
void Count(int i);
}
interface IListCounter: IList, ICounter {}
class C
{
void Test(IListCounter x)
{
x.Count(1); // Error
x.Count = 1; // Error
((IList)x).Count = 1; // Ok, invokes IList.Count.set
((ICounter)x).Count(1); // Ok, invokes ICounter.Count
}
}
88. Write one code example for compile time binding and one for run time binding? What is early/late
binding?
An object is early bound when it is assigned to a variable declared to be of a specific object type. Early bound objects
allow the compiler to allocate memory and perform other optimizations before an application executes.
' Create a variable to hold a new object.
Dim FS As FileStream
' Assign a new object to the variable.
FS = New FileStream("C:\tmp.txt", FileMode.Open)
By contrast, an object is late bound when it is assigned to a variable declared to be of type Object. Objects of this type
can hold references to any object, but lack many of the advantages of early-bound objects.
Dim xlApp As Object
xlApp = CreateObject("Excel.Application")
89. Can you explain what inheritance is and an example of when you might use it?
90. How can you write a class to restrict that only one object of this class can be created (Singleton
class)?
Access specifiers)
91. What are the access-specifiers available in c#?
Private, Protected, Public, Internal, Protected Internal.
92. Explain about Protected and protected internal, internal access-specifier?
protected - Access is limited to the containing class or types derived from the containing class.
internal - Access is limited to the current assembly.
protected internal - Access is limited to the current assembly or types derived from the containing class.
Constructor / Destructor
93. Difference between type constructor and instance constructor? What is static constructor, when it
will be fired? And what is its use?
(Class constructor method is also known as type constructor or type initializer)
Instance constructor is executed when a new instance of type is created and the class constructor is executed after the
type is loaded and before any one of the type members is accessed. (It will get executed only 1st time, when we call
any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class
constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention.
A static constructor is used to initialize a class. It is called automatically to initialize the class before the first instance is
created or any static members are referenced.
94. What is Private Constructor? and its use? Can you create instance of a class which has Private
Constructor?
A: When a class declares only private instance constructors, it is not possible for classes outside the program to derive
from the class or to directly create instances of it. (Except Nested classes)
Make a constructor private if:
- You want it to be available only to the class itself. For example, you might have a special constructor used only in the
implementation of your class' Clone method.
- You do not want instances of your component to be created. For example, you may have a class containing nothing
but Shared utility functions, and no instance data. Creating instances of the class would waste memory.
95. I have 3 overloaded constructors in my class. In order to avoid making instance of the class do I
need to make all constructors to private?
(yes)
96. Overloaded constructor will call default constructor internally?
(no)
97. What are virtual destructors?
98. Destructor and finalize
Generally in C++ the destructor is called when objects gets destroyed. And one can explicitly call the destructors in
C++. And also the objects are destroyed in reverse order that they are created in. So in C++ you have control over
the destructors.
In C# you can never call them, the reason is one cannot destroy an object. So who has the control over the destructor
(in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the objects only when necessary. Some
situations of necessity are memory is exhausted or user explicitly calls System.GC.Collect() method.
Points to remember:
1. Destructors are invoked automatically, and cannot be invoked explicitly.
2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may be declared in it.
4. Destructors cannot be used with structs. They are only used with classes.
5. An instance becomes eligible for destruction when it is no longer possible for any code to use the instance.
6. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for
destruction.
7. When an instance is destructed, the destructors in its inheritance chain are called, in order, from most derived to
least derived.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconfinalizemethodscdestructors.asp
99. What is the difference between Finalize and Dispose (Garbage collection)
Class instances often encapsulate control over resources that are not managed by the runtime, such as window
handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way
to free those resources. Provide implicit control by implementing the protected Finalize Method on an object
(destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point
after there are no longer any valid references to the object.
In some cases, you might want to provide programmers using an object with the ability to explicitly release these
external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better
performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To
provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the
object should call this method when it is done using the object. Dispose can be called even if other references to the
object are alive.
Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the
Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to
call Dispose.
100. What is close method? How its different from Finalize & Dispose?
**
101. What is boxing & unboxing?
102. What is check/uncheck?
103. What is the use of base keyword? Tell me a practical example for base keywords usage?
104. What are the different .net tools which u used in projects?
105. try
{
...
}
catch
{
...//exception occurred here. What'll happen?
}
finally
{
..
}
Ans : It will throw exception.
106. What will do to avoid prior case?
Ans:
try
{
try
{
...
}
catch
{
...
//exception occurred here.
}
finally
{
...
}
}
catch
{
...
}
finally
{
...
}
try
{
...
}
catch
{
...
}
finally
{
..
}
107. Will it go to finally block if there is no exception happened?
Ans: Yes. The finally block is useful for cleaning up any resources allocated in the try block. Control is always passed to
the finally block regardless of how the try block exits.
108. Is goto statement supported in C#? How about Java?
Gotos are supported in C#to the fullest. In Java goto is a reserved keyword that provides absolutely no functionality.
109. Whats different about switch statements in C#?
No fall-throughs allowed. Unlike the C++ switch statement, C# does not support an explicit fall through from one case
label to another. If you want, you can use goto a switch-case, or goto default.
case 1:
cost += 25;
break;
case 2:
cost += 25;
goto case 1;
ADO.NET
110. Advantage of ADO.Net?
ADO.NET Does Not Depend On Continuously Live Connections
Database Interactions Are Performed Using Data Commands
Data Can Be Cached in Datasets
Datasets Are Independent of Data Sources
Data Is Persisted as XML
Schemas Define Data Structures
111. How would u connect to database using .NET?
SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated Security=SSPI;" + "Initial
Catalog=northwind");
nwindConn.Open();
112. What are relation objects in dataset and how & where to use them?
In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another,
to navigate through the tables, and to return child or parent rows from a related table. Adding a DataRelation to a
DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.
The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains
a column named CustID, which serves as a link between the two DataTable objects. The example adds a single
DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the
DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child
DataColumn.
custDS.Relations.Add("CustOrders",
custDS.Tables["Customers"].Columns["CustID"],
custDS.Tables["Orders"].Columns["CustID"]);
OR
private void CreateRelation()
{
// Get the DataColumn objects from two DataTable objects in a DataSet.
DataColumn parentCol;
DataColumn childCol;
// Code to get the DataSet not shown here.
parentCol = DataSet1.Tables["Customers"].Columns["CustID"];
childCol = DataSet1.Tables["Orders"].Columns["CustID"];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation("CustomersOrders", parentCol, childCol);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);
}
113. Difference between OLEDB Provider and SqlClient ?
Ans: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The
SqlClient data provider is fast. It's faster than the Oracle provider, and faster than accessing database via the OleDb
layer. It's faster because it accesses the native library (which automatically gives you better performance), and it was
written with lots of help from the SQL Server team.
114. What are the different namespaces used in the project to connect the database? What data
providers available in .net to connect to database?
System.Data.OleDb classes that make up the .NET Framework Data Provider for OLE DB-compatible data
sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and
read the results.
System.Data.SqlClient classes that make up the .NET Framework Data Provider for SQL Server, which allows
you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is
similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow
you to access ODBC data source in the managed space.
System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes
allow you to access an Oracle data source in the managed space.
115. Difference between DataReader and DataAdapter / DataSet and DataAdapter?
You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the
DataReader can increase application performance and reduce system overhead because only one row at a time is ever
in memory.
After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to
retrieve rows from a data source, as shown in the following example.
SqlDataReader myReader = myCommand.ExecuteReader();
You use the Read method of the DataReader object to obtain a row from the results of the query.
while (myReader.Read())
Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
The DataSet is a memory-resident representation of data that provides a consistent relational programming model
regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to
manage data local to the application. The DataSet represents a complete set of data including related tables,
constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the
relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema
definition language (XSD) schema.
The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The
DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data
source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting
to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its
associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its
associated OleDbCommand and OleDbConnection objects.
116. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Fill()
117. Explain different methods and Properties of DataReader which you have used in your project?
Read
GetString
GetInt32
while (myReader.Read())
Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
118. What happens when we issue Dataset.ReadXml command?
Reads XML schema and data into the DataSet.
119. In how many ways we can retrieve table records count? How to find the count of records in a
dataset?
foreach(DataTable thisTable in myDataSet.Tables){
// For each row, print the values of each column.
foreach(DataRow myRow in thisTable.Rows){
120. How to check if a datareader is closed or opened?
IsClosed()
121. What happens when u try to update data in a dataset in .NET while the record is already deleted in SQL
SERVER as backend?
OR What is concurrency? How will you avoid concurrency when dealing with dataset? (One user deleted one row after
that another user through his dataset was trying to update same row. What will happen? How will you avoid the
problem?)
**
122. How do you merge 2 datasets into the third dataset in a simple manner? OR If you are executing these
statements in commandObject. "Select * from Table1;Select * from Table2 how you will deal result set?
**
123. How do you sort a dataset?
**
124. If a dataset contains 100 rows, how to fetch rows between 5 and 15 only?
**
125. Differences between dataset.clone and dataset.copy?
Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy
any data.
Copy - Copies both the structure and data for this DataSet.
126. What is the use of parameter object?
**
127. How to generate XML from a dataset and vice versa?
**
128. What is method to get XML and schema from Dataset?
ans: getXML () and get Schema ()
129. How do u implement locking concept for dataset?
**
ASP.NET
130. Asp.net and asp differences?
Code Render Block Code Declaration Block
Compiled
Request/Response Event Driven
Object Oriented - Constructors/Destructors, Inheritance, overloading..
Exception Handling - Try, Catch, Finally
Down-level Support
Cultures
User Controls
In-built client side validation
Session - weren't transferable across servers It can span across servers, It can survive server crashes, can work
with browsers that don't support cookies
built on top of the window & IIS, it was always a separate entity & its functionality was limited. its an integral part
of OS under the .net framework. It shares many of the same objects that traditional applications would use, and all
.net objects are available for asp.net's consumption.
Garbage Collection
Declare variable with datatype
In built graphics support
Cultures
131. How ASP and ASP.NET page works? Explain about asp.net page life cycle?
**
132. Order of events in an asp.net page? Control Execution Lifecycle?
Phase What a control needs to do Method or event to override
Initialize Initialize settings needed during the lifetime of the incoming Web request. Init event (OnInit method)
Load view state At the end of this phase, the ViewState property of a control is automatically populated as described
in Maintaining State in a Control. A control can override the default implementation of the LoadViewState method to
customize state restoration. LoadViewState method
Process postback data Process incoming form data and update properties accordingly. LoadPostData method (if
IPostBackDataHandler is implemented)
Load Perform actions common to all requests, such as setting up a database query. At this point, server controls in
the tree are created and initialized, the state is restored, and form controls reflect client-side data. Load event
(OnLoad method)
Send postback change notifications Raise change events in response to state changes between the current and
previous postbacks. RaisePostDataChangedEvent method (if IPostBackDataHandler is implemented)
Handle postback events Handle the client-side event that caused the postback and raise appropriate events on the
server. RaisePostBackEvent method(if IPostBackEventHandler is implemented)
Prerender Perform any updates before the output is rendered. Any changes made to the state of the control in
the prerender phase can be saved, while changes made in the rendering phase are lost. PreRender event
(OnPreRender method)
Save state The ViewState property of a control is automatically persisted to a string object after this stage. This
string object is sent to the client and back as a hidden variable. For improving efficiency, a control can override the
SaveViewState method to modify the ViewState property. SaveViewState method
Render Generate output to be rendered to the client. Render method
Dispose Perform any final cleanup before the control is torn down. References to expensive resources such as database
connections must be released in this phase. Dispose method
Unload Perform any final cleanup before the control is torn down. Control authors generally perform cleanup in
Dispose and do not handle this event. UnLoad event (On UnLoad method)
133. Note To override an EventName event, override the OnEventName method (and call base.
OnEventName).
(Session/State)
134. Application and Session Events
The ASP.NET page framework provides ways for you to work with events that can be raised when your application
starts or stops or when an individual user's session starts or stops:
Application events are raised for all requests to an application. For example, Application_BeginRequest is
raised when any Web Forms page or XML Web service in your application is requested. This event allows you to
initialize resources that will be used for each request to the application. A corresponding event,
Application_EndRequest, provides you with an opportunity to close or otherwise dispose of resources used for the
request.
Session events are similar to application events (there is a Session_OnStart and a Session_OnEnd event), but
are raised with each unique session within the application. A session begins when a user requests a page for the first
time from your application and ends either when your application explicitly closes the session or when the session
times out.
You can create handlers for these types of events in the Global.asax file.
135. Difference between ASP Session and ASP.NET Session?
asp.net session supports cookie less session & it can span across multiple servers.
136. What is cookie less session? How it works?
By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. If
cookies are not available, a session can be tracked by adding a session identifier to the URL. This can be enabled by
setting the following:
http://samples.gotdotnet.com/quickstart/aspplus/doc/stateoverview.aspx
137. How you will handle session when deploying application in more than a server? Describe session
handling in a webfarm, how does it work and what are the limits?
By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does.
Additionally, ASP.NET can store session data in an external process, which can even reside on another machine. To
enable this feature:
Start the ASP.NET state service, either using the Services snap-in or by executing "net start aspnet_state" on
the command line. The state service will by default listen on port 42424. To change the port, modify the registry key
for the service: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\Port
Set the mode attribute of the
Configure the stateConnectionString attribute with the values of the machine on which you started
aspnet_state.
The following sample assumes that the state service is running on the same machine as the Web server ("localhost")
and uses the default port (42424):
mode="StateServer"
stateConnectionString="tcpip=localhost:42424"
/>
Note that if you try the sample above with this setting, you can reset the Web server (enter iisreset on the command
line) and the session state value will persist. **
138. What method do you use to explicitly kill a users session?
Abandon()
139. What are the different ways you would consider sending data across pages in ASP (i.e between
1.asp to 2.asp)?
Session
public properties
140. What is State Management in .Net and how many ways are there to maintain a state in .Net? What
is view state?
Web pages are recreated each time the page is posted to the server. In traditional Web programming, this would
ordinarily mean that all information associated with the page and the controls on the page would be lost with each
round trip.
To overcome this inherent limitation of traditional Web programming, the ASP.NET page framework includes various
options to help you preserve changes that is, for managing state. The page framework includes a facility called view
state that automatically preserves property values of the page and all the controls on it between round trips.
However, you will probably also have application-specific values that you want to preserve. To do so, you can use one
of the state management options.
Client-Based State Management Options:
View State
Hidden Form Fields
Cookies
Query Strings
Server-Based State Management Options
Application State
Session State
Database Support
141. What are the disadvantages of view state / what are the benefits?
Automatic view-state management is a feature of server controls that enables them to repopulate their property values
on a round trip (without you having to write any code). This feature does impact performance, however, since a server
control's view state is passed to and from the server in a hidden form field. You should be aware of when view state
helps you and when it hinders your page's performance.
142. When maintaining session through Sql server, what is the impact of Read and Write operation on
Session objects? will performance degrade?
Maintaining state using database technology is a common practice when storing user-specific information where the
information store is large. Database storage is particularly useful for maintaining long-term state or state that must be
preserved even if the server must be restarted.
**
143. What are the contents of cookie?
**
144. How do you create a permanent cookie?
**
145. What is ViewState? What does the "EnableViewState" property do? Why would I want it on or off?
**
146. Explain the differences between Server-side and Client-side code?
Server side code will process at server side & it will send the result to client. Client side code (javascript) will execute
only at client side.
147. Can you give an example of what might be best suited to place in the Application_Start and Session_Start
subroutines?
**
148. Which ASP.NET configuration options are supported in the ASP.NET implementation on the shared web hosting
platform?
A: Many of the ASP.NET configuration options are not configurable at the site, application or subdirectory level on the
shared hosting platform. Certain options can affect the security, performance and stability of the server and, therefore
cannot be changed. The following settings are the only ones that can be changed in your sites web.config file (s):
browserCaps
clientTarget
pages
customErrors
globalization
authorization
authentication
webControls
webServices
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconaspnetconfiguration.asp
149. Briefly describe the role of global.asax?
150. How can u debug your .net application?
151. How do u deploy your asp.net application?
152. Where do we store our connection string in asp.net application?
153. Various steps taken to optimize a web based application (caching, stored procedure etc.)
154. How does ASP.NET framework maps client side events to Server side events.
Security
155. Security types in ASP/ASP.NET? Different Authentication modes?
156. How .Net has implemented security for web applications?
157. How to do Forms authentication in asp.net?
158. Explain authentication levels in .net ?
159. Explain autherization levels in .net ?
160. What is Role-Based security?
A role is a named set of principals that have the same privileges with respect to security (such as a teller or a
manager). A principal can be a member of one or more roles. Therefore, applications can use role membership to
determine whether a principal is authorized to perform a requested action.
**
161. How will you do windows authentication and what is the namespace? If a user is logged under integrated
windows authentication mode, but he is still not able to logon, what might be the possible cause for this? In ASP.Net
application how do you find the name of the logged in person under windows authentication?
162. What are the different authentication modes in the .NET environment?
loginUrl="url"
protection="All|None|Encryption|Validation"
timeout="30" path="/" >
requireSSL="true|false"
slidingExpiration="true|false">
Attribute Option Description
mode Controls the default authentication mode for an application.
Windows Specifies Windows authentication as the default authentication mode. Use this mode when
using any form of Microsoft Internet Information Services (IIS) authentication: Basic, Digest, Integrated Windows
authentication (NTLM/Kerberos), or certificates.
Forms Specifies ASP.NET forms-based authentication as the default authentication mode.
Passport Specifies Microsoft Passport authentication as the default authentication mode.
None Specifies no authentication. Only anonymous users are expected or applications can handle events to
provide their own authentication.
163. How do you specify whether your data should be passed as Query string and Forms (Mainly about
POST and GET)
Through attribute tag of form tag.
164. What is the other method, other than GET and POST, in ASP.NET?
165. What are validator? Name the Validation controls in asp.net? How do u disable them? Will the asp.net
validators run in server side or client side? How do you do Client-side validation in .Net? How to disable validator
control by client side JavaScript?
A set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-
defined requirements. Validation controls perform input checking in server code. If the user is working with a browser
that supports DHTML, the validation controls can also perform validation ("EnableClientScript" property set to
true/false) using client script.
The following validation controls are available in asp.net:
RequiredFieldValidator Control, CompareValidator Control, RangeValidator Control, RegularExpressionValidator Control,
CustomValidator Control, ValidationSummary Control.
166. Which two properties are there on every validation control?
ControlToValidate, ErrorMessage
167. How do you use css in asp.net?
Within the section of an HTML document that will use these styles, add a link to this external CSS style sheet
that
follows this form:
MyStyles.css is the name of your external CSS style sheet.
168. How do you implement postback with a text box? What is postback and usestate?
Make AutoPostBack property to true
169. How can you debug an ASP page, without touching the code?
170. What is SQL injection?
An SQL injection attack "injects" or manipulates SQL code by adding unexpected SQL to a query.
Many web pages take parameters from web user, and make SQL query to the database. Take for instance when a user
login, web page that user name and password and make SQL query to the database to check if a user has valid name
and password.
Username: ' or 1=1 ---
Password: [Empty]
This would execute the following query against the users table:
select count(*) from users where userName='' or 1=1 --' and userPass=''
171. How can u handle Exceptions in Asp.Net?
172. How can u handle Un Managed Code Exceptions in ASP.Net?
173. Asp.net - How to find last error which occurred?
A: Server.GetLastError();
[C#]
Exception LastError;
String ErrMessage;
LastError = Server.GetLastError();
if (LastError != null)
ErrMessage = LastError.Message;
else
ErrMessage = "No Errors";
Response.Write("Last Error = " + ErrMessage);
174. How to do Caching in ASP?
A: <%@ OutputCache Duration="60" VaryByParam="None" %>
VaryByParam value Description
none One version of page cached (only raw GET)
* n versions of page cached based on query string and/or POST body
v1 n versions of page cached based on value of v1 variable in query string or POST body
v1;v2 n versions of page cached based on value of v1 and v2 variables in query string or POST body
175. <%@ OutputCache Duration="60" VaryByParam="none" %>
<%@ OutputCache Duration="60" VaryByParam="*" %>
<%@ OutputCache Duration="60" VaryByParam="name;age" %>
The OutputCache directive supports several other cache varying options
VaryByHeader - maintain separate cache entry for header string changes (UserAgent, UserLanguage, etc.)
VaryByControl - for user controls, maintain separate cache entry for properties of a user control
VaryByCustom - can specify separate cache entries for browser types and version or provide a custom
GetVaryByCustomString method in HttpApplicationderived class
176. What is the Global ASA(X) File?
177. Any alternative to avoid name collisions other then Namespaces.
A scenario that two namespaces named N1 and N2 are there both having the same class say A. now in another class i
ve written
using N1;using N2;
and i am instantiating class A in this class. Then how will u avoid name collisions?
Ans: using alias
Eg: using MyAlias = MyCompany.Proj.Nested;
178. Which is the namespace used to write error message in event Log File?
179. What are the page level transaction and class level transaction?
180. What are different transaction options?
181. What is the namespace for encryption?
182. What is the difference between application and cache variables?
183. What is the difference between control and component?
184. You ve defined one page_load event in aspx page and same page_load event in code behind how will prog
run?
185. Where would you use an IHttpModule, and what are the limitations of any approach you might take in
implementing one?
186. Can you edit data in the Repeater control? Which template must you provide, in order to display data in a
Repeater control? How can you provide an alternating color scheme in a Repeater control? What property must you
set, and what method must you call in your code, in order to bind the data from some data source to the Repeater
control?
187. What is the use of web.config? Difference between machine.config and Web.config?
ASP.NET configuration files are XML-based text files--each named web.config--that can appear in any directory on an
ASP.NET
Web application server. Each web.config file applies configuration settings to the directory it is located in and to all
virtual child directories beneath it. Settings in child directories can optionally override or modify settings specified in
parent directories. The root configuration file--WinNT\Microsoft.NET\Framework\
provides
default configuration settings for the entire machine. ASP.NET configures IIS to prevent direct browser access to
web.config
files to ensure that their values cannot become public (attempts to access them will cause ASP.NET to return 403:
Access
Forbidden).
At run time ASP.NET uses these web.config configuration files to hierarchically compute a unique collection of settings
for
each incoming URL target request (these settings are calculated only once and then cached across subsequent
requests; ASP.NET
automatically watches for file changes and will invalidate the cache if any of the configuration files change).
http://samples.gotdotnet.com/quickstart/aspplus/doc/configformat.aspx
188. What is the use of sessionstate tag in the web.config file?
Configuring session state: Session state features can be configured via the
To double the default timeout of 20 minutes, you can add the following to the web.config file of an application:
189. What are the different modes for the sessionstates in the web.config file?
Off Indicates that session state is not enabled.
Inproc Indicates that session state is stored locally.
StateServer Indicates that session state is stored on a remote server.
SQLServer Indicates that session state is stored on the SQL Server.
190. What is smart navigation?
When a page is requested by an Internet Explorer 5 browser, or later, smart navigation enhances the user's
experience of the page by performing the following:
eliminating the flash caused by navigation.
persisting the scroll position when moving from page to page.
persisting element focus between navigations.
retaining only the last page state in the browser's history.
Smart navigation is best used with ASP.NET pages that require frequent postbacks but with visual content that does
not change dramatically on return. Consider this carefully when deciding whether to set this property to true.
Set the SmartNavigation attribute to true in the @ Page directive in the .aspx file. When the page is requested, the
dynamically generated class sets this property.
191. In what order do the events of an ASPX page execute. As a developer is it important to undertsand these
events?
192. How would you get ASP.NET running in Apache web servers - why would you even do this?
193. What tags do you need to add within the asp:datagrid tags to bind columns manually
194. What base class do all Web Forms inherit from?
System.Web.UI.Page
195. How can we create pie chart in asp.net?
196. Is it possible for me to change my aspx file extension to some other name?
Yes.
Open IIS->Default Website -> Properties
Select HomeDirectory tab
Click on configuration button
Click on add. Enter aspnet_isapi details (C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\aspnet_isapi.dll |
GET,HEAD,POST,DEBUG)
Open machine.config(C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\CONFIG) & add new extension under
197. What is AutoEventWireup attribute for ?
WEBSERVICE & REMOTING
198. What is a WebService and what is the underlying protocol used in it? Namespace?
Web Services are applications delivered as a service on the Web. Web services allow for programmatic access of
business logic over the Web. Web services typically rely on XML-based protocols, messages, and interface descriptions
for communication and access. Web services are designed to be used by other programs or applications rather than
directly by end user. Programs invoking a Web service are called clients. SOAP over HTTP is the most commonly used
protocol for invoking Web services.
199. Why Web Services?
By exposing data and functionality using standard protocols, Web services make it easy to build sophisticated
applications that integrate many features and content. There are three main uses of Web services. Application
integration Web services within an intranet are commonly used to integrate business applications running on disparate
platforms. For example, a .NET client running on Windows 2000 can easily invoke a Java Web service running on a
mainframe or Unix machine to retrieve data from a legacy application. Business integration Web services allow trading
partners to engage in e-business leveraging the existing Internet infrastructure. Organizations can send electronic
purchase orders to suppliers and receive electronic invoices. Doing e-business with Web services means a low barrier
to entry because Web services can be added to existing applications running on any platform without changing legacy
code. Commercial Web services focus on selling content and business services to clients over the Internet similar to
familiar Web pages. Unlike Web pages, commercial Web services target applications not humans as their direct users.
Continental Airlines exposes flight schedules and status Web services for travel Web sites and agencies to use in their
applications. Like Web pages, commercial Web services are valuable only if they expose a valuable service or content.
It would be very difficult to get customers to pay you for using a Web service that creates business charts with the
customers? data. Customers would rather buy a charting component (e.g. COM or .NET component) and install it on
the same machine as their application. On the other hand, it makes sense to sell real-time weather information or
stock quotes as a Web service. Technology can help you add value to your services and explore new markets, but
ultimately customers pay for contents and/or business services, not for technology
200. In a Webservice, need to display 10 rows from a table. So DataReader or DataSet is best choice?
A: WebService will support only DataSet.
201. Are Web Services a replacement for other distributed computing platforms?
No. Web Services is just a new way of looking at existing implementation platforms.
202. What is SOAP, WSDL, UDDI and the concept behind Web Services? What are various components of
WSDL? What is the use of WSDL.exe utility?
SOAP is an XML-based messaging framework specifically designed for exchanging formatted data across the Internet,
for example using request and reply messages or sending entire documents. SOAP is simple, easy to use, and
completely neutral with respect to operating system, programming language, or distributed computing platform.
After SOAP became available as a mechanism for exchanging XML messages among enterprises (or among disparate
applications within the same enterprise), a better way was needed to describe the messages and how they are
exchanged. The Web Services Description Language (WSDL) is a particular form of an XML Schema, developed by
Microsoft and IBM for the purpose of defining the XML message, operation, and protocol mapping of a web service
accessed using SOAP or other XML protocol. WSDL defines web services in terms of "endpoints" that operate on XML
messages. The WSDL syntax allows both the messages and the operations on the messages to be defined abstractly,
so they can be mapped to multiple physical implementations. The current WSDL spec describes how to map messages
and operations to SOAP 1.1, HTTP GET/POST, and MIME. WSDL creates web service definitions by mapping a group of
endpoints into a logical sequence of operations on XML messages. The same XML message can be mapped to multiple
operations (or services) and bound to one or more communications protocols (using "ports").
The Universal Description, Discovery, and Integration (UDDI) framework defines a data model (in XML) and SOAP APIs
for registration and searches on business information, including the web services a business exposes to the Internet.
UDDI is an independent consortium of vendors, founded by Microsoft, IBM, and Ariba, for the purpose of developing an
Internet standard for web service description registration and discovery. Microsoft, IBM, and Ariba also are hosting the
initial deployment of a UDDI service, which is conceptually patterned after DNS (the Internet service that translates
URLs into TCP addresses). UDDI uses a private agreement profile of SOAP (i.e. UDDI doesn't use the SOAP
serialization format because it's not well suited to passing complete XML documents (it's aimed at RPC style
interactions). The main idea is that businesses use the SOAP APIs to register themselves with UDDI, and other
businesses search UDDI when they want to discover a trading partner, for example someone from whom they wish to
procure sheet metal, bolts, or transistors. The information in UDDI is categorized according to industry type and
geographical location, allowing UDDI consumers to search through lists of potentially matching businesses to find the
specific one they want to contact. Once a specific business is chosen, another call to UDDI is made to obtain the
specific contact information for that business. The contact information includes a pointer to the target business's WSDL
or other XML schema file describing the web service that the target business publishes.
203. How to generate proxy class other than .net app and wsdl tool?
To access an XML Web service from a client application, you first add a Web reference, which is a reference to an XML
Web service. When you create a Web reference, Visual Studio creates an XML Web service proxy class automatically
and adds it to your project. This proxy class exposes the methods of the XML Web service and handles the marshalling
of appropriate arguments back and forth between the XML Web service and your application. Visual Studio uses the
Web Services Description Language (WSDL) to create the proxy.
To generate an XML Web service proxy class:
From a command prompt, use Wsdl.exe to create a proxy class, specifying (at a minimum) the URL to an XML
Web service or a service description, or the path to a saved service description.
Wsdl /language:language /protocol:protocol /namespace:myNameSpace /out:filename
/username:username /password:password /domain:domain
204. asynchronous web service means?
205. What are the events fired when web service called?
206. How does SOAP transport happen and what is the role of HTTP in it? How you can access a webservice using
soap?
207. How will do transaction in Web Services?
208. What are the different formatters can be used in both? Why?.. binary/soap
209. What is a proxy in web service? How do I use a proxy server when invoking a Web service?
If you are using the SOAP Toolkit, you need to set some connector properties to use a proxy server: Dim soap As
SoapClient Set soap=New SoapClient soap.ConnectorProperty("ProxyServer") = ?proxyservername?
soap.ConnectorProperty("ProxyPort") = ?8080? soap.ConnectorProperty("UseProxy") = True While with .NET , you just
need to create a System.Net.WebProxy object and use it to set the Proxy property Dim webs As localhost.MyService()
webs.Proxy=New System.Net.WebProxy(?http://proxyserver:8080?)
210. How you will protect / secure a web service?
For the most part, things that you do to secure a Web site can be used to secure a Web Service. If you need to encrypt
the data exchange, you use Secure Sockets Layer (SSL) or a Virtual Private Network to keep the bits secure. For
authentication, use HTTP Basic or Digest authentication with Microsoft Windows integration to figure out who the
caller is.
these items cannot:
Parse a SOAP request for valid values
Authenticate access at the Web Method level (they can authenticate at the Web Service level)
Stop reading a request as soon as it is recognized as invalid
http://msdn.microsoft.com/library/default.asp?url=/library/en-
us/cpguide/html/cpcontransactionsupportinaspnetwebservices.asp
211. How will you expose/publish a webservice?
212. Whats the attribute for webservice method? What is the namespace for creating webservice?
213. What is disco file?
214. What is Remoting?
The process of communication between different operating system processes, regardless of whether they are on the
same computer. The .NET remoting system is an architecture designed to simplify communication between objects
living in different application domains, whether on the same computer or not, and between different contexts, whether
in the same application domain or not.
215. Difference between web services & remoting?
ASP.NET Web Services .NET Remoting
Protocol Can be accessed only over HTTP Can be accessed over any protocol (including TCP, HTTP, SMTP and
so on)
State Management Web services work in a stateless environment Provide support for both stateful and
stateless environments through Singleton and SingleCall objects
Type System Web services support only the datatypes defined in the XSD type system, limiting the number of
objects that can be serialized. Using binary communication, .NET Remoting can provide support for rich type system
Interoperability Web services support interoperability across platforms, and are ideal for heterogeneous environments.
.NET remoting requires the client be built using .NET, enforcing homogenous environment.
Reliability Highly reliable due to the fact that Web services are always hosted in IIS Can also take advantage of
IIS for fault isolation. If IIS is not used, application needs to provide plumbing for ensuring the reliability of the
application.
Extensibility Provides extensibility by allowing us to intercept the SOAP messages during the serialization and
deserialization stages. Very extensible by allowing us to customize the different components of the .NET remoting
framework.
Ease-of-Programming Easy-to-create and deploy. Complex to program.
216. Though both the .NET Remoting infrastructure and ASP.NET Web services can enable cross-process
communication, each is designed to benefit a different target audience. ASP.NET Web services provide a simple
programming model and a wide reach. .NET Remoting provides a more complex programming model and has a much
narrower reach.
As explained before, the clear performance advantage provided by TCPChannel-remoting should make you think about
using this channel whenever you can afford to do so. If you can create direct TCP connections from your clients to your
server and if you need to support only the .NET platform, you should go for this channel. If you are going to go cross-
platform or you have the requirement of supporting SOAP via HTTP, you should definitely go for ASP.NET Web
services.
Both the .NET remoting and ASP.NET Web services are powerful technologies that provide a suitable framework for
developing distributed applications. It is important to understand how both technologies work and then choose the one
that is right for your application. For applications that require interoperability and must function over public networks,
Web services are probably the best bet. For those that require communications with other .NET components and where
performance is a key priority, .NET Remoting is the best choice. In short, use Web services when you need to send and
receive data from different computing platforms, use .NET Remoting when sending and receiving data between .NET
applications. In some architectural scenarios, you might also be able to use.NET Remoting in conjunction with ASP.NET
Web services and take advantage of the best of both worlds.
The Key difference between ASP.NET webservices and .NET Remoting is how they serialize data into messages and the
format they choose for metadata. ASP.NET uses XML serializer for serializing or Marshalling. And XSD is used for
Metadata. .NET Remoting relies on System.Runtime.Serialization.Formatter.Binary and
System.Runtime.Serialization.SOAPFormatter and relies on .NET CLR Runtime assemblies for metadata.
217. Can you pass SOAP messages through remoting?
218. CAO and SAO.
Client Activated objects are those remote objects whose Lifetime is directly Controlled by the client. This is in direct
contrast to SAO. Where the server, not the client has complete control over the lifetime of the objects.
Client activated objects are instantiated on the server as soon as the client request the object to be created. Unlike as
SAO a CAO doesnt delay the object creation until the first method is called on the object. (In SAO the object is
instantiated when the client calls the method on the object)
219. singleton and singlecall.
Singleton types never have more than one instance at any one time. If an instance exists, all client requests are
serviced by that instance.
Single Call types always have one instance per client request. The next method invocation will be serviced by a
different server instance, even if the previous instance has not yet been recycled by the system.
220. What is Asynchronous Web Services?
221. How to generate WebService proxy?
222. Web Client class and its methods?
223. Flow of remoting?
(XML)
224. Explain the concept of data island?
225. How to use XML DOM model on client side using JavaScript.
226. What are the ways to create a tree view control using XML, XSL & JavaScript?
227. Questions on XPathNavigator, and the other classes in System.XML Namespace?
228. What is Use of Template in XSL?
229. What is Well Formed XML and Valid XML
230. How you will do SubString in XSL
231. Can we do sorting in XSL ? how do you deal sorting columns dynamically in XML.
232. What is Async property of XML Means ?
233. What is XPath Query ?
234. Difference Between Element and Node.
235. What is CDATA Section.
236. DOM & SAX parsers explanation and difference
237. What is GetElementbyname method will do?
238. What is selectnode method will give?
239. What is valid xml document? What a well formed xml document?
240. What is the Difference between XmlDocument and XmlDataDocument?
241. Explain what a DiffGram is, and a good use for one?
A DiffGram is an XML format that is used to identify current and original versions of data elements. When sending and
retrieving a DataSet from an XML Web service, the DiffGram format is implicitly used.
The DataSet uses the DiffGram format to load and persist its contents, and to serialize its contents for transport across
a network connection. When a DataSet is written as a DiffGram, it populates the DiffGram with all the necessary
information to accurately recreate the contents, though not the schema, of the DataSet, including column values from
both the Original and Current row versions, row error information, and row order.
DiffGram Format
The DiffGram format is divided into three sections: the current data, the original (or "before") data, and an errors
section, as shown in the following example.
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
The DiffGram format consists of the following blocks of data:
The name of this element, DataInstance, is used for explanation purposes in this documentation. A DataInstance
element represents a DataSet or a row of a DataTable. Instead of DataInstance, the element would contain the name
of the DataSet or DataTable. This block of the DiffGram format contains the current data, whether it has been modified
or not. An element, or row, that has been modified is identified with the diffgr:hasChanges annotation.
This block of the DiffGram format contains the original version of a row. Elements in this block are matched to
elements in the DataInstance block using the diffgr:id annotation.
block. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation.
242. If I replace my Sqlserver with XML files and how about handling the same?
243. Write syntax to serialize class using XML Serializer?
IIS
244. In which process does IIS runs (was asking about the EXE file)
inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET
request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the
request to the actual worker process aspnet_wp.exe.
245. Where are the IIS log files stored?
C:\WINDOWS\system32\Logfiles\W3SVC1
OR
c:\winnt\system32\LogFiles\W3SVC1
246. What are the different IIS authentication modes in IIS 5.0 and Explain? Difference between basic
and digest authentication modes?
IIS provides a variety of authentication schemes:
Anonymous (enabled by default)
Basic
Digest
Integrated Windows authentication (enabled by default)
Client Certificate Mapping
Anonymous
Anonymous authentication gives users access to the public areas of your Web site without prompting them for a user
name or password. Although listed as an authentication scheme, it is not technically performing any client
authentication because the client is not required to supply any credentials. Instead, IIS provides stored credentials to
Windows using a special user account, IUSR_machinename. By default, IIS controls the password for this account.
Whether or not IIS controls the password affects the permissions the anonymous user has. When IIS controls the
password, a sub authentication DLL (iissuba.dll) authenticates the user using a network logon. The function of this DLL
is to validate the password supplied by IIS and to inform Windows that the password is valid, thereby authenticating
the client. However, it does not actually provide a password to Windows. When IIS does not control the password, IIS
calls the LogonUser() API in Windows and provides the account name, password and domain name to log on the user
using a local logon. After the logon, IIS caches the security token and impersonates the account. A local logon makes
it possible for the anonymous user to access network resources, whereas a network logon does not.
Basic Authentication
IIS Basic authentication as an implementation of the basic authentication scheme found in section 11 of the HTTP 1.0
specification.
As the specification makes clear, this method is, in and of itself, non-secure. The reason is that Basic authentication
assumes a trusted connection between client and server. Thus, the username and password are transmitted in clear
text. More specifically, they are transmitted using Base64 encoding, which is trivially easy to decode. This makes Basic
authentication the wrong choice to use over a public network on its own.
Basic Authentication is a long-standing standard supported by nearly all browsers. It also imposes no special
requirements on the server side -- users can authenticate against any NT domain, or even against accounts on the
local machine. With SSL to shelter the security credentials while they are in transmission, you have an authentication
solution that is both highly secure and quite flexible.
Digest Authentication
The Digest authentication option was added in Windows 2000 and IIS 5.0. Like Basic authentication, this is an
implementation of a technique suggested by Web standards, namely RFC 2069 (superceded by RFC 2617).
Digest authentication also uses a challenge/response model, but it is much more secure than Basic authentication
(when used without SSL). It achieves this greater security not by encrypting the secret (the password) before sending
it, but rather by following a different design pattern -- one that does not require the client to transmit the password
over the wire at all.
Instead of sending the password itself, the client transmits a one-way message digest (a checksum) of the user's
password, using (by default) the MD5 algorithm. The server then fetches the password for that user from a Windows
2000 Domain Controller, reruns the checksum algorithm on it, and compares the two digests. If they match, the server
knows that the client knows the correct password, even though the password itself was never sent. (If you have ever
wondered what the default ISAPI filter "md5filt" that is installed with IIS 5.0 is used for, now you know.
Integrated Windows Authentication
Integrated Windows authentication (formerly known as NTLM authentication and Windows NT Challenge/Response
authentication) can use either NTLM or Kerberos V5 authentication and only works with Internet Explorer 2.0 and later.
When Internet Explorer attempts to access a protected resource, IIS sends two WWW-Authenticate headers, Negotiate
and NTLM.
If Internet Explorer recognizes the Negotiate header, it will choose it because it is listed first. When using
Negotiate, the browser will return information for both NTLM and Kerberos. At the server, IIS will use Kerberos if both
the client (Internet Explorer 5.0 and later) and server (IIS 5.0 and later) are running Windows 2000 and later, and
both are members of the same domain or trusted domains. Otherwise, the server will default to using NTLM.
If Internet Explorer does not understand Negotiate, it will use NTLM.
So, which mechanism is used depends upon a negotiation between Internet Explorer and IIS.
When used in conjunction with Kerberos v5 authentication, IIS can delegate security credentials among computers
running Windows 2000 and later that are trusted and configured for delegation. Delegation enables remote access of
resources on behalf of the delegated user.
Integrated Windows authentication is the best authentication scheme in an intranet environment where users have
Windows domain accounts, especially when using Kerberos. Integrated Windows authentication, like digest
authentication, does not pass the user's password across the network. Instead, a hashed value is exchanged.
Client Certificate Mapping
A certificate is a digitally signed statement that contains information about an entity and the entity's public key, thus
binding these two pieces of information together. A trusted organization (or entity) called a Certification Authority (CA)
issues a certificate after the CA verifies that the entity is who it says it is. Certificates can contain different types of
data. For example, an X.509 certificate includes the format of the certificate, the serial number of the certificate, the
algorithm used to sign the certificate, the name of the CA that issued the certificate, the name and public key of the
entity requesting the certificate, and the CA's signature. X.509 client certificates simplify authentication for larger user
bases because they do not rely on a centralized account database. You can verify a certificate simply by examining the
certificate.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsent7/html/vxconIISAuthentication.asp
247. How to configure the sites in Web server (IIS)?
248. Advantages in IIS 6.0?
http://www.microsoft.com/windowsserver2003/iis/evaluation/features/default.mspx
http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/windowsserver2003/proddocs/datacenter/gs_whatschanged.asp
249. IIS Isolation Levels?
Internet Information Server introduced the notion "Isolation Level", which is also present in IIS4 under a different
name. IIS5 supports three isolation levels, that you can set from the Home Directory tab of the site's Properties dialog:
Low (IIS Process): ASP pages run in INetInfo.Exe, the main IIS process, therefore they are executed in-
process. This is the fastest setting, and is the default under IIS4. The problem is that if ASP crashes, IIS crashes as
well and must be restarted (IIS5 has a reliable restart feature that automatically restarts a server when a fatal error
occurs).
Medium (Pooled): In this case ASP runs in a different process, which makes this setting more reliable: if ASP
crashes IIS won't. All the ASP applications at the Medium isolation level share the same process, so you can have a
web site running with just two processes (IIS and ASP process). IIS5 is the first Internet Information Server version
that supports this setting, which is also the default setting when you create an IIS5 application. Note that an ASP
application that runs at this level is run under COM+, so it's hosted in DLLHOST.EXE (and you can see this executable
in the Task Manager).
High (Isolated): Each ASP application runs out-process in its own process space, therefore if an ASP
application crashes, neither IIS nor any other ASP application will be affected. The downside is that you consume more
memory and resources if the server hosts many ASP applications. Both IIS4 and IIS5 supports this setting: under IIS4
this process runs inside MTS.EXE, while under IIS5 it runs inside DLLHOST.EXE.
When selecting an isolation level for your ASP application, keep in mind that out-process settings - that is, Medium and
High - are less efficient than in-process (Low). However, out-process communication has been vastly improved under
IIS5, and in fact IIS5's Medium isolation level often deliver better results than IIS4's Low isolation. In practice, you
shouldn't set the Low isolation level for an IIS5 application unless you really need to serve hundreds pages per second.
Controls
250. How will you do Redo and Undo in a TextControl?
251. How to implement DataGrid in .NET? How would u make a combo-box appear in one column of a DataGrid?
What are the ways to show data grid inside a data grid for a master details type of tables? If we write any code for
DataGrid methods, what is the access specifier used for that methods in the code behind file and why?
252. How can we create Tree control in asp.net?
Programming
253. Write a program in C# for checking a given number is PRIME or not.
254. Write a program to find the angle between the hours and minutes in a clock
255. Write a C# program to find the Factorial of n
256. How do I upload a file from my ASP.NET page?
A: In order to perform file upload in your ASP.NET page, you will need to use two classes: the
System.Web.UI.HtmlControls.HtmlInputFile class and the System.Web.HttpPostedFile class. The HtmlInputFile class
represents and HTML input control that the user will use on the client side to select a file to upload. The HttpPostedFile
class represents the uploaded file and is obtained from the PostedFile property of the HtmlInputFile class. In order to
use the HtmlInputFile control, you need to add the enctype attribute to your form tag as follows:
257. How do I send an email message from my ASP.NET page?
A: You can use the System.Web.Mail.MailMessage and the System.Web.Mail.SmtpMail class to send email in your ASPX
pages. Below is a simple example of using this class to send mail in C# and VB.NET. In order to send mail through our
mail server, you would want to make sure to set the static SmtpServer property of the SmtpMail class to mail-fwd.
C#
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.Mail" %>
Technical Note
Constructors in C# :
Broadly speaking, it is a method in the class which gets executed when its object is created. Usually we put the
initialization code in the constructor. Writing a constructor in the class is pretty simple, have a look at the following
sample :
public class mySampleClass
{
public mySampleClass()
{
// This is the constructor method.
}
// rest of the class members goes here.
}
When the object of this class is instantiated this constructor will be executed. Something like this :
mySampleClass obj = new mySampleClass()
// At this time the code in the constructor will // be executed
Constructor Overloading :
C# supports overloading of constructors, that means we can have constructors with different set of parameters. So our
class can be like this :
public class mySampleClass
{
public mySampleClass()
{
// This is the no parameter constructor method.
// First Constructor
}
public mySampleClass(int Age)
{
// This is the constructor with one parameter.
// Second Constructor
}
public mySampleClass(int Age, string Name)
{
// This is the constructor with two parameters.
// Third Constructor
}
// rest of the class members goes here.
}
Well, note here that call to the constructor now depends on the way you instantiate the object. For example :
mySampleClass obj = new mySampleClass()
// At this time the code of no parameter
// constructor (First Constructor) will be executed
mySampleClass obj = new mySampleClass(12)
// At this time the code of one parameter
// constructor(Second Constructor) will be
// executed.
The call to the constructors is completely governed by the rules of the overloading here.
Calling Constructor from another Constructor:
You can always make the call to one constructor from within the other. Say for example :
public class mySampleClass
{
public mySampleClass(): this(10)
{
// This is the no parameter constructor method.
// First Constructor
}
public mySampleClass(int Age)
{
// This is the constructor with one parameter.
// Second Constructor
}
}
Very first of all let us see what is this syntax :
public mySampleClass(): this(10)
Here this refers to same class, so when we say this(10), we actually mean execute the public mySampleClass(int Age)
method.The above way of calling the method is called initializer. We can have at the most one initializer in this way in
the method.
Another thing which we must know is the execution sequence i.e., which method will be executed when. Here if I
instantiate the object as mySampleClass obj = new mySampleClass()
Then the code of public mySampleClass(int Age) will be executed before the code of mySampleClass(). So practically
the definition of the method :
public mySampleClass(): this(10)
{
// This is the no parameter constructor method.
// First Constructor
}
is equivalent to
public mySampleClass()
{
mySampleClass(10)
// This is the no parameter constructor method.
// First Constructor
}
Note that only this and base (we will see it further) keywords are allowed in initializers, other method calls will raise
the error.
This is sometimes called Constructor chaining.
Behavior of Constructors in Inheritance :
Let us first create the inherited class.
public class myBaseClass
{
public myBaseClass()
{
// Code for First Base class Constructor
}
public myBaseClass(int Age)
{
// Code for Second Base class Constructor
}
// Other class members goes here
}
public class myDerivedClass : myBaseClass
// Note that I am inheriting the class here.
{
public myDerivedClass()
{
// Code for the First myDerivedClass Constructor.
}
public myDerivedClass(int Age):base(Age)
{
// Code for the Second myDerivedClass Constructor.
}
// Other class members goes here
}
Now what will be the execution sequence here :
If I create the object of the Derived class as
myDerivedClass obj = new myDerivedClass()
Then the sequence of execution will be
1. public myBaseClass() method.
2. and then public myDerivedClass() method.
Note: If we do not provide initializer referring to the base class constructor then it executes the no parameter
constructor of the base class.
Note one thing here : We are not making any explicit call to the constructor of base class neither by initializer nor by
the base() keyword, but it is still executing. This is the normal behavior of the constructor.
If I create the object of the Derived class as myDerivedClass obj = new myDerivedClass(15)
Then the sequence of execution will be
1. public myBaseClass(int Age) method.
2. and then public myDerivedClass(int Age) method.
Here the new keyword base has come into picture. This refers to the base class of the current class. So, here it refers
to the myBaseClass. And base(10) refers to the call to myBaseClass(int Age) method.
Also note the usage of Age variable in the syntax : public myDerivedClass(int Age):base(Age). [ Understanding it is left
to the reader.
Static Constructors :
This is a new concept introduced in C#. By new here I mean that it was not available for the C++ developers. This is a
special constructor and gets called before the first object is created of the class. The time of execution cannot be
determined, but it is definitely before the first object creation - could be at the time of loading the assembly.
The syntax of writing the static constructors is also damn simple. Here it is :
public class myClass
{
static myClass()
{
// Initialization code goes here.
// Can only access static members here.
}
// Other class methods goes here
}
Notes for Static Constructors :
1. There can be only one static constructor in the class.
2. The static constructor should be without parameters.
3. It can only access the static members of the class.
4. There should be no access modifier in static constructor definition.
Ok fine, all the above points are fine but why is it like that? Let us go step by step here.
Firstly, the call to the static method is made by the CLR and not by the object, so we do not need to have the access
modifier to it.
Secondly, it is going to be called by CLR, who can pass the parameters to it, if required, No one, so we cannot have
parameterized static constructor.
Thirdly, Non-static members in the class are specific to the object instance so static constructor, if allowed to work on
non-static members, will reflect the changes in all the object instances, which is impractical. So static constructor can
access only static members of the class.
Fourthly, Overloading needs the two methods to be different in terms to methods definition, which you cannot do with
Static Constructors, so you can have at the most one static constructor in the class.
Now, one question raises here, can we have the two constructors as
public class myClass
{
static myClass()
{
// Initialization code goes here.
// Can only access static members here.
}
public myClass()
{
// Code for the First myDerivedClass Constructor.
}
// Other class methods goes here
}
This is perfectly valid, though doesnt seem to be in accordance with overloading concepts. But why? Because the time
of execution of the two method are different. One is at the time of loading the assembly and one is at the time of
object creation.
FAQs Regd. Constructors :
1. Is the Constructor mandatory for the class ?
Yes, It is mandatory to have the constructor in the class and that too should be
accessible for the object i.e., it should have a proper access modifier. Say for example
we have the private constructor in the class then it is of no use as it cannot be
accessed by the object, so practically it is no available for the object. In such
conditions it will raise an error.
2. What if I do not write the constructor ?
In such case the compiler will try to supply the no parameter constructor for your
class behind the scene. Compiler will attempt this only if you do not write the
constructor for the class. If you provide any constructor ( with or without parameters),
then compiler will not make any such attempt.
3. What if I have the constructor public myDerivedClass() but not the public myBaseClass() ?
It will raise an error. If either the no parameter constructor is absent or it is in-
accessible ( say it is private ), it will raise an error. You will have to take the precaution
here.
4. Can we access static members from the non-static ( normal ) constructors ?
Yes, We can. There is no such restriction on non-static constructors. But there is one
on static constructors that it can access only static members.
2)Static Constructor in C# and their Usages
C# supports two types of constructor, a class constructor (static constructor) and an instance constructor (non-static
constructor).
Static constructor is used to initialize static data members as soon as the class is referenced
first time, whereas an instance constructor is used to create an instance of that class with
static data member of a class.
Since static constructor is a class constructor, they are guaranteed to be called as soon as we refer to that class or by
creating an instance of that class.You may say, why not initialize static data members where we declare them in the
code. Like this :
private static int id = 10;
private static string name = "jack";
Static data members can certainly be initialized at the time of their declaration but there are times when value of one
static member may depend upon the value of another static member. In such cases we definitely need some
mechanism to handle conditional initialization of static members. To handlesuch situation, C# provides static
constructor.
Let me explain you with examples ://File Name : Test.cs
using System;
namespace Constructor
{
class Test
{
//Declaration and initialization of static data member
private static int id = 5;
public static int Id
{
get
{
return id;
}
}
public static void print()
{
Console.WriteLine("Test.id = " + id);
}
static void Main(string[] args)
{
//Print the value of id
Test.print();
}
}
}
In the above example, static data member
program your output would look similar to this :Test.id = 5
Lets create one more class similar to class Test but this time the value of its static data member would depend on the
value of static data member
//File Name : Test1.cs
using System;
namespace Constructor
{
class Test1
{
private static int id ;
//Static constructor, value of data member id is set conditionally here.
//This type of initialization is not possible at the time of declaration.
static Test1()
{
if( Test.Id < 10 )
{
id = 20;
}
else
{
id = 100;
}
Console.WriteLine("Static
}
public static void print()
{
Console.WriteLine("Test1.id = " + id);
}
static void Main(string[] args)
{
//Print the value of id
Test1.print();
}
}
}
As you can see in the above static constructor, static data member
initialization is not possible at the time of declaration. This is where static constructor comes in picture. So if you
compile and run this program your output would look similar to this :
Static
.id = 20
Since
Some important point regarding static constructor from C# Language Specification and C# Programmer's Reference :
1) The static constructor for a class executes before any instance of the class is created.
2) The static constructor for a class executes before any of the static members for the class are referenced.
3) The static constructor for a class executes after the static field initializers (if any) for the class.
4) The static constructor for a class executes at most one time during a single program instantiation
5) A static constructor does not take access modifiers or have parameters.
6) A static constructor is called automatically to initialize the class before the first instance is created or any static
members are referenced.
7) A static constructor cannot be called directly.
8) The user has no control on when the static constructor is executed in the program.
9) A typical use of static constructors is when the class is using a log file and the constructor is used to write entries to
this file.
Hopefully, this would clear the confusion some of developers have about static constructor.
Global Assembly Cache
To create a small Class Library project by using Visual Studio .NET or Visual Studio 2005, to generate a strong name,
and to install the .dll file of the project in the GAC, follow these steps:
1. In Visual Studio .NET or in Visual Studio 2005, create a new Visual C# Class Library project, and name the
project GACDemo.
2. You must use a strong name. To generate this cryptographic key-pair, use the SN Tool. This tool is located in
the \bin subdirectory where the .NET Framework Solution Developer Kit (SDK) is installed. The SN Tool is easy to use.
The command-line statement takes the following
form:sn -k "[DriveLetter]:\[DirectoryToPlaceKey]\[KeyName].snk"
3. Create a directory named GACKey in C:\ so that you can easily locate the key, and access the key from the
command prompt.
Note For most users, the .NET tools are located in C:\Program Files\Microsoft.NET\FrameworkSDK\Bin. Before you
type the following SN command, you may want to copy this similar path on your computer to the .NET bin directory.
Type cd from the command prompt, right-click to paste the path, and then press ENTER to quickly change to the
directory where the SN Tool is located.
Type the following:
sn -k "C:\GACKey\GACkey.snk"
4. A key is generated, but it is not yet associated with the assembly of the project. To create this association,
double-click the AssemblyInfo.cs file in Visual Studio .NET Solution Explorer. This file has the list of assembly attributes
that are included by default when a project is created in Visual Studio .NET. Modify the AssemblyKeyFile assembly
attribute in the code as follows:
[assembly: AssemblyKeyFile("C:\\GACKey\\GACKey.snk")]
Compile the project by clicking CTRL+SHIFT+B. You do not have to have any additional code to install a .dll file in the
GAC.
5. You can install the .dll file by using the Gacutil Tool, or by dragging the .dll file to the appropriate directory. If
you use the Gacutil Tool, you can use the following command:
gacutil -I "[DriveLetter]:\[PathToBinDirectoryInVSProject]\gac.dll"
If you want to drag the file, use Microsoft Windows Explorer. Open two instances of Windows Explorer. In one instance,
find the location of the .dll file output for your console project. In the other instance, find c:\[SystemRoot]\Assembly.
Drag your .dll file to the Assembly folder.
Complete Code Listing (AssemblyInfo.cs)
using System.Reflection;
using System.Runtime.CompilerServices;
//
// General Information about an assembly is controlled through the following
// set of attributes. Change these attribute values to modify the information
// that is associated with an assembly.
//
[assembly: AssemblyTitle("")]
[assembly: AssemblyDescription("")]
[assembly: AssemblyConfiguration("")]
[assembly: AssemblyCompany("")]
[assembly: AssemblyProduct("")]
[assembly: AssemblyCopyright("")]
[assembly: AssemblyTrademark("")]
[assembly: AssemblyCulture("")]
//
// Version information for an assembly is made up of the following four values:
//
// Major Version
// Minor Version
// Build Number
// Revision
//
// You can specify all the values, or you can default the revision and build numbers
// by using the '*' as shown below:
[assembly: AssemblyVersion("1.0.*")]
//
// To sign your assembly you must specify a key to use. See the
// Microsoft .NET Framework documentation for more information about assembly signing.
//
// Use the following attributes to control that key is used for signing.
//
// Notes:
// (*) If no key is specified, the assembly is not signed.
// (*) KeyName refers to a key that has been installed in the Crypto Service
// Provider (CSP) on your computer. KeyFile refers to a file that contains
// a key.
// (*) If the KeyFile and the KeyName values are both specified, the
// following processing occurs:
// (1) If the KeyName can be found in the CSP, that key is used.
// (2) If the KeyName does not exist and the KeyFile does exist, the key
// in the KeyFile is installed to the CSP and used.
// (*) To create a KeyFile, you can use the sn.exe (Strong Name) utility.
// When specifying the KeyFile, the location of the KeyFile must be
// relative to the project output directory which is
// %Project Directory%\obj\
// located in the project directory, you would specify the AssemblyKeyFile
// attribute as [assembly: AssemblyKeyFile("..\\..\\mykey.snk")]
// (*) Delay Signing is an advanced option - see the Microsoft .NET Framework
// documentation for more information about this.
//
[assembly: AssemblyDelaySign(false)]
[assembly: AssemblyKeyFile("C:\\GACKey\\GACKey.snk")]
[assembly: AssemblyKeyName("")]
Verification
1. Start Windows Explorer.
2. Locate C:\SystemRoot\ assembly.
3. You see GACDemo in the list of installed .dll files.
An assembly is a fundamental building block of any .NET Framework application. For example, when you build a simple
C# application, Visual Studio creates an assembly in the form of a single portable executable (PE) file, specifically an
EXE or DLL.
Assemblies contain metadata that describe their own internal version number and details of all the data and object
types they contain. For more information see Assembly Manifest.
Assemblies are only loaded as they are required. If they are not used, they are not loaded. This means that assemblies
can be an efficient way to manage resources in larger projects.
Assemblies can contain one or more modules. For example, larger projects may be planned in such a way that several
individual developers work on separate modules, all coming together to create a single assembly. For more information
on modules, see the topic How to: Build a Multifile Assembly.
Assemblies Overview
Assemblies have the following properties:
Assemblies are implemented as .exe or .dll files.
You can share an assembly between applications by placing it in the Global Assembly Cache.
Assemblies must be strong-named before they can be placed in the Global Assembly Cache. For more
information, see Strong-Named Assemblies.
Assemblies are only loaded into memory if they are required.
You can programmatically obtain information about an assembly using reflection. For more information, see
the topic Reflection.
If you want to load an assembly only to inspect it, use a method such as ReflectionOnlyLoadFrom.
You can use two versions of the same assembly in a single application. For more information, see extern alias.
Assembly Manifest
Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the
assembly relate to each other. The assembly manifest contains this assembly metadata. An assembly manifest
contains all the metadata needed to specify the assembly's version requirements and security identity, and all
metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly
manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a
standalone PE file that contains only assembly manifest information.
The following illustration shows the different ways the manifest can be stored.
Types of assemblies
For an assembly with one associated file, the manifest is incorporated into the PE file to form a single-file assembly.
You can create a multifile assembly with a standalone manifest file or with the manifest incorporated into one of the PE
files in the assembly.
Each assembly's manifest performs the following functions:
Enumerates the files that make up the assembly.
Governs how references to the assembly's types and resources map to the files that contain their declarations
and implementations.
Enumerates other assemblies on which the assembly depends.
Provides a level of indirection between consumers of the assembly and the assembly's implementation details.
Renders the assembly self-describing.
Assembly Manifest Contents
The following table shows the information contained in the assembly manifest. The first four itemsthe assembly
name, version number, culture, and strong name informationmake up the assembly's identity.
Information Description
Assembly name A text string specifying the assembly's name.
Version number A major and minor version number, and a revision and build number. The common language runtime
uses these numbers to enforce version policy.
Culture Information on the culture or language the assembly supports. This information should be used only to
designate an assembly as a satellite assembly containing culture- or language-specific information. (An assembly with
culture information is automatically assumed to be a satellite assembly.)
Strong name information The public key from the publisher if the assembly has been given a strong name.
List of all files in the assembly A hash of each file contained in the assembly and a file name. Note that all files that
make up the assembly must be in the same directory as the file containing the assembly manifest.
Type reference information Information used by the runtime to map a type reference to the file that contains its
declaration and implementation. This is used for types that are exported from the assembly.
Information on referenced assemblies A list of other assemblies that are statically referenced by the assembly.
Each reference includes the dependent assembly's name, assembly metadata (version, culture, operating system, and
so on), and public key, if the assembly is strong named.
What Is a Satellite Assembly?
A definition from MSDN says something like this: "A .NET Framework assembly containing resources specific to a given
language. Using satellite assemblies, you can place the resources for different languages in different assemblies, and
the correct assembly is loaded into memory only if the user elects to view the application in that language."
This means that you develop your application in a default language and add flexibility to react with change in the
locale. Say, for example, you developed your application in an en-US locale. Now, your application has multilingual
support. When you deploy your code in, say, India, you want to show labels, messages shown in the national language
which is other than English.
Satellite assemblies give this flexibility. You create any simple text file with translated strings, create resources, and
put them into the bin\debug folder. That's it. The next time, your code will read the CurrentCulture property of the
current thread and accordingly load the appropriate resource.
This is called the hub and spoke model. It requires that you place resources in specific locations so that they can be
located and used easily. If you do not compile and name resources as expected, or if you do not place them in the
correct locations, the common language runtime will not be able to locate them. As a result, the runtime uses the
default resource set.
Creating a Satellite Assembly
1. Create a folder with a specific culture name (for example, en-US) in the application's bin\debug folder.
2. Create a .resx file in that folder. Place all translated strings into it.
3. Create a .resources file by using the following command from the .NET command prompt. (localizationsample
is the name of the application namespace. If your application uses a nested namespace structure like
MyApp.YourApp.MyName.YourName as the type of namespace, just use the uppermost namespace for creating
resources filesMyApp.)
4. resgen Strings.en-US.resx LocalizationSample.
5. Strings.en-US.resources
6. al /embed:LocalizationSample.Strings.en-US.resources
7. /out:LocalizationSample.resources.dll /c:en-US
The above step will create two files, LocalizationSample.Strings.en-US.resources and LocalizationSample.resources.dll.
Here, LocalizationSample is the name space of the application.
8. In the code, find the user's language; for example, en-US. This is culture specific.
9. Give the assembly name as the name of .resx file. In this case, it is Strings.
Using a Satellite Assembly
Follow these steps:
Thread.CurrentThread.CurrentCulture =
CultureInfo.CreateSpecificCulture(specCult);
Thread.CurrentThread.CurrentUICulture =
new CultureInfo(specCult);
ResourceManager resMgr =
new ResourceManager(typeof(Form1).Namespace + "." +
asmName, this.GetType().Assembly);
btnTest.Text = resMgr.GetString("Jayant");
That's it. See how simple is it to create a satellite assembly and use it in your code.
Here's how to use a satellite assembly if your assembly is a strong named assembly. When you create an assembly
with a string name, all the assemblies it refers to must have a strong name. This is true with a satellite assembly also.
Here are the steps to create a strong named satellite assembly.
String Naming a Satellite Assembly
al /embed:ExploreDotNet2005.Strings.en-US.resources
/out:ExploreDotNet2005.resources.dll /c:en-US
/template:../ExploreDotNet2005.exe /keyfile:../../..
/KeyPair.snk
Remember that /template is very important because it inherits the parent assembly manifest, and the strong name
key pair must be the same as that for the running assembly. I've tried using different strong names for satellite
assembly and executing the assembly. but it throws an exception.
String VS Stringbuilder
This is my second article regarding performance. Most of the people use string everywhere in their code. Actually when
doing string concatenation, do you know what exactly your doing? It has a big drawback mainly in concatenation which
can be overcome by StringBuilder. It will give vast improvement in performance when you use concatenation of string
over String.
What is the exact difference?
First we will look at what happens when you concatenate two strings. For a rough idea, think like this. In a loop you
are adding few numbers to get a string to give all the numbers.
string returnNumber = "";
for(int i = 0; i<1000; i++)
{
returnNumber = returnNumber + i.ToString();
}
Here we are defining a string called returnNumber and after that in the loop we are concatenating the old one with the
new to get a string. Do you know when we do like that we are assigning it again and again? I mean its really like
assigning 999 new strings!
Actually the concatenation will create a new string returnNumber, with both old returnNumber and i.ToString(). If we
think roughly, How will be the performance of the code? Can you imagine it? No one things about this when coding.
If we can have something which are be defined only once and add all the strings into it, what can you say about the
performance. That's what StringBuilder is doing.
StringBuilder returnNumber = new StringBuilder(10000);
for(int i = 0; i<1000; i++)
{
returnNumber.Append(i.ToString());
}
We are creating a StringBuilder of length 10000 in memory where we can add all the strings. Which surely wont create
a new string each and every time. Actually we are creating a StringBinder, where whenever something added it will get
copied in to that memory area. At the end we can get the string by StringBuilder.ToString(). Here also it wont create a
new string. It will return a string instance that will point to the string inside the StringBuilder. See, How efficient this
is?
To explain this with some practical I'm not going to analyze IL code or Optimized JIT compiled code. You can see the
different by running the samples.
Why string? Can't use StringBinder everywhere?
No. You can't. When initializing a StringBuilder you are going down in performance. Also many actions that you do with
string can't be done with StringBinder. Actually it is used mostly for situations as explained above. Last week I show a
person, who used StringBuilder to just add two strings together! its really nonsense. We must really think about the
overhead of initialization. In my personal experience a StringBuilder can be used where more than four or more string
concatenation take place. Also if you try to do some other manipulation (Like removing a part from the string,
replacing a part in the string, etc, etc) then better not to use StringBuilder at those places. Because anyway we are
creating new strings. Another important issue. We must be careful to guess the size of StringBuilder . If the size which
we are going to get is more than what assigned, it must increase the size. Which will reduce the performance of it.
http://www.codeproject.com/Purgatory/string.asp
B)
As far as reasoning, MS docs suggest it is for use in loops.
"The String object is immutable. Every time you use one of the methods in the System.String class, you create a new
string object in memory, which requires a new allocation of space for that new object. In situations where you need to
perform repeated modifications to a string, the overhead associated with creating a new String object can be costly.
The System.Text.StringBuilder class can be used when you want to modify a string without creating a new object. For
example, using the StringBuilder class can boost performance when concatenating many strings together in a loop."
So, to answer the question, at what point is it more efficient, I wrote a little tester. The StringBuilder returned Sub-
10ms times (DateTime not capable of registering < 10ms) at 1000 or fewer iterations of a loop simply appending the
string "string". The += method of concatenation takes 15+ms for the same iterations. At 5000 iterations, the +=
method was becoming much slower at 218ms. versus the StringBuilder which was still sub 10ms.Even at 10000
iterations, the SB was sub 10, while the concat method had gone over 1.2 seconds. My test code is as follows:
private void UpdateTime()
{
int iterations = Int32.Parse(txtIterations.Text);
string theString = txtTheString.Text;
DateTime strCall = DateTime.Now;
string targetString = null;
for(int x = 0 ; x < iterations ; x++)
{targetString += theString;}
TimeSpan time = (DateTime.Now - strCall);
txtConcatTime.Text = time.TotalMilliseconds.ToString();
//StringBuilder
DateTime inCall = DateTime.Now;
StringBuilder sb = new StringBuilder(theString);
for(int x = 0 ; x < iterations ; x++)
{
sb.Append(theString);
}
time = (DateTime.Now - inCall);
txtStringBTime.Text = time.TotalMilliseconds.ToString();
MessageBox.Show("done");
}
Application Domain
What is an application domain?
Application domain is a construct in the CLR that is the unit of isolation for an application. The isolation guarantees the
following:
An application can be independently stopped.
An application cannot directly access code or resources in another application.
A fault in an application cannot affect other applications.
Configuration information is scoped by application. This means that an application controls the location from
which code is loaded and the version of the code that is loaded.
For more information see COM+ Application Domains.
What is the difference between an application domain and a process?
An application domain is lighter than a process. Application domains are appropriate for scenarios that require isolation
without the heavy cost associated with running an application within a process. A process runs exactly one application.
In contrast, the CLR allows multiple applications to be run in a single process by loading them into separate application
domains. Additionally, the CLR verifies that user code in an application domain is type safe.
For more information see COM+ Application Domains.
What is a CLR host?
The Windows operating system does not provide support for running a CLR application. That support is provided by a
CLR host. A CLR host is an application that is responsible for loading the CLR into a process, creating application
domains within the process, and executing user code within the application domains. Examples of hosts that ship with
the .NET Framework include:
ASP.NET. An ISAPI filter that ships with ASP.NET loads the CLR and does the initialization necessary to handle
web requests.
Internet Explorer. A MIME filter hooks into Internet Explorer versions 5.01 and higher to execute managed
controls referenced from HTML pages.
Shell Executables. When a managed application is launched from a shell, a small piece of unmanaged code loads
the CLR and transitions control of the application to the CLR.
For more information see Hosting the Common Language Runtime.
What is a default domain?
The default domain is an application domain that is created automatically by the CLR every time it is initialized in a
process. The default domain is not unloaded until the process shuts down. Most hosts dont run code in the default
domain for two main reasons. First, the default domain cannot be shut down independently of the process. Second, for
security and isolation reasons, it is desirable that the user code and hosting code execute in different application
domains. Instead, hosts create application domains with a set of properties that control security, isolation, loading, etc.
What is an assembly?
An assembly is a reusable, versionable, self-describing deployment unit for types and resources it is the primary
building block of a .NET application. Assemblies provide the infrastructure to allow the runtime to fully understand the
contents of an application and to enforce the versioning and dependency rules defined by the application.
An assembly consists of the following two logical elements:
The sets of types and resources that form some logical unit of functionality.
A manifest which is the metadata that describes how the types and resources relate and what they depend on to
work properly.
For more information see Assembly Overview.
How do I run managed code in a process?
The first step in running managed code in a process is to get the CLR loaded and initialized using a CLR host. Typically,
a host consists of both managed code and unmanaged code. The managed code which executes in the default domain
is usually responsible for creating the application domains in which the user code exists. All CLR hosts must contain
unmanaged code because execution must begin in unmanaged code. The .NET Frameworks provides a set of
unmanaged APIs that the host can use to configure the CLR, load the CLR into a process, load the hosts managed code
into the default domain, and transition from the unmanaged code to the managed code.
The second step in running managed code in a process is to create application domains in which the user code will
execute. The creator of the application domain can specify criteria which control code isolation, security, and loading of
assemblies.
The third step in running managed code in a process is to execute user code in one or more application domains
created in the previous step. All code that is run in the CLR must be part of an assembly. There are three options for
loading assemblies. First, precompiled assemblies can be loaded from disk. Second, precompiled assemblies can be
loaded from an array of bytes. Third, assemblies can be built dynamically in an application domain using the BCL
Reflection Emit APIs.
Note. For an application launched from the command-line, the shell host executes the steps described above on behalf
of the user and hides the complexity from the user.
For more information see Hosting the Common Language Runtime.
What is the purpose of the System._AppDomain interface?
The System._AppDomain interface is meant for use by unmanaged code that needs access to the members of the
managed System.AppDomain class. Unmanaged code calls the methods of the System._AppDomain interface through
COM Interop. Unmanaged code can obtain a pointer to the _AppDomain interface by calling QueryInterface on the
default domain. See Hosting the Common Language Runtime and Common Language Runtime Hosting Interfaces for
details.
How do I create an application domain?
The default domain is created automatically when a CLR hosts unmanaged code calls the CLR hosting interface to load
the CLR.
A user application domain is created by calling one of the following overloaded static methods of the
System.AppDomain class:
1. public static AppDomain CreateDomain(String friendlyName)
2. public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo)
3. public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
4. public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String
appRelativeSearchPath, bool shadowCopyFiles)
Overload 1 allows an application domain to be created given its name. Overloads 2-3 allow a
System.Security.Policy.Evidence object to be supplied to CreateDomain to define the security policy for the application.
Overload 3 allows a System.AppDomainSetup object to be supplied to CreateDomain to configure how assemblies are
loaded into the application domain. Overload 4 allows some of the common configuration settings to be specified as
parameters without defining a System.AppDomainSetup object.
How do I configure how assemblies are loaded into an application domain?
An application domain is configured by supplying a System.AppDomainSetup object to the following static method of
the System.AppDomain class:
public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
The AppDomainSetup class provides a set of properties that can be set or retrieved. The properties control how
assemblies are loaded into an application domain. The most important properties are ApplicationBase and
ConfigurationFile. The other properties are used mainly by a CLR host and are described in the BCL documentation. A
newly created application domain inherits the ApplicationBase property of its creator. No other property is inherited by
the new application domain.
The ApplicationBase property defines the root directory for an application. When an assembly needs to be loaded from
the disk, the CLR will begin probing for the assembly in the directory specified by the ApplicationBase property. This
provides a degree of isolation in that the assemblies that are loaded are privatized to a particular application.
The ConfigurationFile property defines the XML file that contains the configuration settings for the application that
executes in the application domain. The configuration file describes information such as versioning rules and policies
for locating types. For more information see Configuration Files for the CLR.
The following code snippet creates an application domain with default security policy and specific ApplicationBase and
ConfigurationFile properties:
// C# Sample Code
using System;
AppDomainSetup info = new AppDomainSetup();
info.ApplicationBase = C:\\Program Files\\MyApp;
info.ConfigurationFile = C:\\Program Files\\MyApp\\MyApp.exe.config;
AppDomain appDomain = AppDomain.CreateDomain(MyDomain, null, info);
How do I retrieve configuration information about an an application domain?
Use the following property of the System.AppDomain class.
public AppDomainSetup SetupInformation { get; }
How do I define the security policy for an application domain?
The runtime enforces code-access security. In code-access security, what code is allowed to do is based on the
characteristics of the code called Evidence. The runtime maps the evidence to a set of permissions when the code is
loaded and run. The permissions control specific actions of the code.
A host can control policy in two ways:
First, the host can provide evidence to an application domain when it is created by supplying an Evidence object to
System.AppDomain.CreateDomain. This supplied evidence is added to the evidence for the code before the security
policy for the code is evaluated. For example, the following code snippet restricts code running in an application
domain associated with a Web site to no more permissions than code originating from the site:
// C# Sample Code
using System;
using System.Security.Policy;
Evidence evidence = new Evidence();
Evidence.AddHost(new URL(http:://www.site.com);
AppDomain appDomain = AppDomain.CreateDomain(MyDomain, evidence);
Second, the host can restrict the permissions granted at a specific policy level. The hierarchy of policy levels beginning
at the top level are: enterprise wide policy, machine wide policy, per user policy, and application domain level policy.
Each policy level can restrict the permissions granted by the level above it. The
System.AppDomain.SetAppDomainPolicy is used to specify security policy. For more information and an example of
how to use the method, see Hosting the Common Language Runtime.
How do I retrieve the evidence for an application domain?
Use the following property of the System.AppDomain class.
public Evidence Evidence { get; }
How do I execute an application in a remote application domain?
The System.AppDomain class provides the following methods that can be used to run an assembly in an application
domain:
1. public int ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
2. public int ExecuteAssembly(String assemblyFile, Evidence assemblySecurity)
3. public int ExecuteAssembly(String assemblyFile)
Overload 1 is the most general form of ExecuteAssembly. The first parameter is the path name of the assembly to be
executed. The second parameter allows the caller to supply a System.Security.Policy.Evidence object for the assembly.
The last parameter allows the caller to supply an array of parameters to be passed to main entry point of the
assembly.
The steps necessary to execute an assembly in a remote application domain are as follows:
Create the remote application domain using System.AppDomain.CreateDomain. Optionally specify the following:
o Configuration information such as ApplicationBase to control where assemblies are searched for during loading.
o Evidence to control specific actions of the code executed in the application domain.
Execute the assembly using System.AppDomain.ExecuteAssembly on the application domain created in the
previous step.
Note that the ExecuteAssembly method will not work with executables generated by Visual C++ compiler due to the
way the unmanaged CRT startup works.
The following code snippet shows how to execute an assembly named HelloWorld1:
// C# Sample Code
// File: ExecAssembly.cs
// Creates a remote application domain and executes an assembly
// within that application domain.
using System;
using System.Reflection;
using System.Runtime.Remoting;
public class ExecAssembly
{
public static void Main( String[] argv )
{
// Set ApplicationBase to the current directory
AppDomainSetup info = new AppDomainSetup();
info.ApplicationBase = "file:///" + System.Environment.CurrentDirectory;
// Create an application domain with null evidence
AppDomain dom = AppDomain.CreateDomain("RemoteDomain", null, info);
// Tell the AppDomain to execute the assembly
dom.ExecuteAssembly("HelloWorld1.exe");
// Clean up by unloading the application domain
AppDomain.Unload(dom);
}
}
The HelloWorld1 assembly contains the following code:
// C# Sample Code
// File: HelloWorld1.cs
using System;
using System.Threading;
public class HelloWorld
{
public void SayHello(String greeting)
{
Console.WriteLine("In the application domain: " + Thread.GetDomain().FriendlyName);
Console.WriteLine(greeting);
}
public static void Main( String[] argv )
{
HelloWorld o = new HelloWorld();
o.SayHello("Hello World!");
}
}
Compile ExecAssemby.cs and HelloWorld1.cs as follows:
csc ExecAssembly.cs
csc HelloWorld1.cs
How do I invoke a method in a remote application domain?
The steps necessary to invoke a method in a remote application domain are as follows:
Create the remote application domain using System.AppDomain.CreateDomain. Optionally specify the following:
o Configuration information such as ApplicationBase to control where assemblies are searched for during loading.
o Evidence to control specific actions of the code executed in the application domain.
Ensure the type containing the method to be invoked derives from System.MarshalByRefObject. This is
necessary to ensure that the type is marshaled by reference across the boundary of the created application domain.
Call System.AppDomain.CreateInstance to create an instance of the parent type of the method in the application
domain created in the previous step. CreateInstance will return a wrapped object reference (ObjectHandle) that needs
to be unwrapped before it can be used.
Unwrap the ObjectHandle to obtain an Object reference to invoke methods on the type.
The System.AppDomain class provides the following methods for instantiating a type:
1. public ObjectHandle CreateInstance(String assemblyName, String typeName)
2. public ObjectHandle CreateInstance(String assemblyName, String typeName, Object[] activationAttributes)
3. public ObjectHandle CreateInstance(String assemblyName, String typeName, bool ignoreCase, BindingFlags
bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence
securityAttributes)
4. public ObjectHandle CreateInstanceFrom(String assemblyFile, String typeName)
5. public ObjectHandle CreateInstanceFrom(String assemblyFile, String typeName, Object[] activationAttributes)
6. public ObjectHandle CreateInstanceFrom(String assemblyFile, String typeName, bool ignoreCase, BindingFlags
bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence
securityAttributes)
The difference between CreateInstance and CreateInstanceFrom is that CreateInstances first parameter is the simple
name of an assembly while the first parameter to CreateInstanceFrom is the path name of the assembly. The first
method calls the static method Assembly.Load while the second method calls the static method Assembly.LoadFrom.
See loading of assemblies for additional details.
The System.AppDomain class also provides the following convenience methods that combine the operations of
instantiating a type and unwrapping the ObjectHandle:
1. public Object CreateInstanceAndUnwrap(String assemblyName, String typeName)
2. public Object CreateInstance(String assemblyName, String typeName, Object[] activationAttributes)
3. public Object CreateInstance(String assemblyName, String typeName, bool ignoreCase, BindingFlags bindingAttr,
Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence securityAttributes)
4. public Object CreateInstanceFromAndUnwrap (String assemblyFile, String typeName)
5. public Object CreateInstanceFromAndUnwrap (String assemblyFile, String typeName, Object[]
activationAttributes)
6. public Object CreateInstanceFromAndUnwrap (String assemblyFile, String typeName, bool ignoreCase,
BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence
securityAttributes)
The following code snippet shows how to invoke the SayHello method in the HelloWorld2 assembly:
// C# Sample Code
// File: Invoke.cs
// Creates a remote application domain and invokes a method
// within an assembly in that application domain.
using System;
using System.Reflection;
using System.Runtime.Remoting;
public class InvokeMethod
{
public static void Main( String[] argv )
{
// Set ApplicationBase to the current directory
AppDomainSetup info = new AppDomainSetup();
info.ApplicationBase = "file:///" + System.Environment.CurrentDirectory;
// Create an application domain with null evidence
AppDomain dom = AppDomain.CreateDomain("RemoteDomain", null, info);
// Load the assembly HelloWorld2 and instantiate the type
// HelloWorld
BindingFlags flags = (BindingFlags.Public | BindingFlags.Instance | BindingFlags.CreateInstance);
ObjectHandle objh = dom.CreateInstance("HelloWorld2", "HelloWorld", false, flags, null, new String[]{"Hello
World!"}, null, null, null);
if (objh == null) {
Console.WriteLine("CreateInstance failed");
return;
}
// Unwrap the object
Object obj = objh.Unwrap();
// Cast to the actual type
HelloWorld h = (HelloWorld)obj;
// Invoke the method
h.SayHello();
// Clean up by unloading the application domain
AppDomain.Unload(dom);
}
}
The HelloWorld2 assembly contains the following code:
// C# Sample Code
// File: HelloWorld2.cs
using System;
using System.Threading;
public class HelloWorld : MarshalByRefObject
{
private String _greeting;
public HelloWorld(String greeting)
{
if (greeting == null) {
throw new ArgumentNullException("Null greeting!");
}
_greeting = greeting;
}
public void SayHello()
{
Console.WriteLine("In the application domain: " + Thread.GetDomain().FriendlyName);
Console.WriteLine(_greeting);
}
}
Compile Invoke.cs and HelloWorld2.cs as follows:
csc /t:library HelloWorld2.cs
csc /r:Helloworld2.exe Invoke.cs
Note. The HelloWorld2 assembly must be locatable in the callers application domain and the remote application
domain. The assembly is loaded into the remote application domain by CreateInstance. It is loaded into the callers
application domain when the Object obj is cast to the HelloWorld type.
Note. If the metadata for the invoked method SayHello is not available in the callers application domain, you may get
errors during JIT compilation.
How do I load an assembly into an application domain?
The System.AppDomain and the System.Reflection.Assembly classes provide many overloads for loading an assembly
into an application domain. The System.AppDomain.Load methods are primarily meant for COM Interoperability use.
However, they can be used safely to load an assembly into the current application domain.
An attempt to call AppDomain.Load on an application domain that is not the current application domain will result in a
successful load of the assembly in the target application domain. Since Assembly objects are not MarshalByRef, when
the method attempts to return the Assembly object for the loaded assembly to the current application domain (i.e., the
callers application domain), the runtime will try to load the specified assembly into the current application domain. The
load may fail if the configuration settings (such as AppDomainSetup.ApplicationBase) for the two application domains
are different. Even when the loading into the current application domain succeeds, the Assembly object that is loaded
into the current application domain is different from the assembly that was loaded into the target application domain.
The System.AppDomain provides the following methods for loading an assembly into an application domain:
1. public Assembly Load(AssemblyName assemblyRef)
2. public Assembly Load(AssemblyName assemblyRef, Evidence evidence)
3. public Assembly Load(AssemblyName assemblyRef, Evidence evidence, String callerLocation)
4. public Assembly Load(byte[] rawAssembly)
5. public Assembly Load(byte[] rawAssembly, byte[] rawAssemblyStore)
6. public Assembly Load(byte[] rawAssembly, byte[] rawAssemblyStore, Evidence evidence)
7. public Assembly Load(String assemblyName)
8. public Assembly Load(String assemblyName, Evidence evidence)
9. public Assembly Load(String assemblyName, Evidence evidence, String callerLocation)
Note. Overloads 3 and 9 are obsolete and will be removed in a future release.
Overloads 1-3 require the caller to supply an System.Reflection.AssemblyName object that specifies what assembly is
to be loaded. See the description of the class in the BCL reference documentation for the details. Overload 2, 6, and 8
allow the caller to supply evidence for the assembly code that will execute in the application domain. Overloads 4-6 are
used to load a COFF-based image containing an emitted assembly and optionally specify the raw bytes representing
the symbols for the assembly. In overloads 7-9, the assemblyName parameter should be an assembly name and not
the path or filename of the requested assembly. assemblyName does not include an extension such as .DLL or .EXE.
Some examples of AssemblyName include the following:
A simply named assembly with a default culture:
com.microsoft.crypto, Culture=
A fully specified reference for strong named assembly with culture en:
com.microsoft.crypto, Culture=en, PublicKeyToken=a5d015c7d5a0b012, Version=1.0.0.0
Partially specified AssemblyName which may be satisfied by either strong or simply named assembly:
com.microsoft.crypto
com.microsoft.crypto, Culture=""
com.microsoft.crypto, Culture=en
The System.Reflection.Assembly class provides the following static methods for loading an assembly into the current
application domain:
1. public static Assembly Load(AssemblyName assemblyRef)
2. public static Assembly Load(AssemblyName assemblyRef, Evidence evidence)
3. public static Assembly Load(AssemblyName assemblyRef, Evidence evidence, String callerLocation)
4. public static Assembly Load(byte[] rawAssembly)
5. public static Assembly Load(byte[] rawAssembly, byte[] rawSymbolStore)
6. public static Assembly Load(byte[] rawAssembly, byte[] rawSymbolStore, Evidence evidence)
7. public static Assembly Load(String assemblyName)
8. public static Assembly Load(String assemblyName, Evidence evidence)
9. public static Assembly Load(String assemblyName, Evidence evidence, String callerLocation)
10.public static Assembly LoadFrom(String assemblyFile)
11.public static Assembly LoadFrom(String assemblyFile, Evidence evidence)
Note. Overloads 3 and 9 are obsolete and will be removed in a future release. Overload 1-9 of Assembly.Load are
similar to the overloads 1-9 of AppDomain.Load with the difference that the static Assembly.Load methods load the
specified assembly into the current application domain while the instance AppDomain.Load methods load the specified
assembly into the target application domain. The same restriction on the assemblyName parameter that applied to
AppDomain.Load also applies to overloads 7-9, i.e., the assembly name should not be a path name or a file name of
the requested assembly and should not contain an extension such as .DLL or .EXE in the name. Overloads 10-11 can
be used to load an assembly from a specific location by specifying a file name or path to the assembly.
Note. To ensure that assemblies loaded using Assembly.LoadFrom do not interfere with direct dependencies of the
managed application (obtained using Assembly.Load), the assembly cache manager maintains separate load contexts,
namely, a default load context and a LoadFrom load context. The default load context records the assembly name and
assembly instance information of the transitive closure of dependent assembies that are directly used by the managed
application. The LoadFrom load context contains the assembly name and assembly instance information for all
assemblies loaded using Assembly.LoadFrom as well as the transitive closure of their dependencies. For more
information about load contexts, consult the SDK documentation.
Note. The System.AppDomain class does not provide LoadFrom methods similar to the System.Assembly.LoadFrom
methods. If you wish to load an assembly into a target application domain given a file name fro an assembly, you will
need to use the following workaround:
Create a stub assembly that calls System.Assembly.LoadFrom using the file name of the assembly to be loaded
into the target application domain.
Execute the stub assembly in the target application domain using System.AppDomain.ExecuteAssembly.
How do I dynamically resolve assemblies, types, and resources?
The assembly resolution is controlled by the configuration properties for the application domain such as
System.AppDomainSetup.ApplicationBase. The configuration properties may not be sufficient in some hosting
scenarios, especially if the host is creating assemblies in memory on the fly using Reflection Emit, since there may not
be an assembly on disk to find. In such cases, you can use the System.AssemblyResolve event to hook into the type
loading process.
The AssemblyResolve event is defined as follows:
public event ResolveEventHandler AssemblyResolve
where System.ResolveEventHandler is defined as follows:
public delegate Assembly ResolveEventHandler(Object sender, ResolveEventArgs args)
The args parameter to ResolveEventHandler is the identity of the assembly the runtime is seeking. The receipient of
the event is free to resolve the reference to the assembly by any means. For example, the receipient may construct an
assembly on the fly, find it in a custom location on disk, etc. The only requirement is that the receipient return a
instance of System.Reflection.Assembly.
The following sample code shows how to define a handler to resolve an assembly dynamically:
// C# Sample Code
// File AssemblyResolve.cs
// Illustrates how to resolve an assembly dynamically.
using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.Remoting;
using System.Threading;
public class AssemblyResolve
{
// This method invokes the "SayHello" method on the
// type "HelloWorld" of an assemby "DynamicHelloWorld".
// The assembly does not exist on the disk but is created
// on the fly by the assembly resolution handler.
public static void Main( String[] argv )
{
// Define the handler for resolving the assembly
AssemblyResolve assemblyResolve = new AssemblyResolve();
ResolveEventHandler hndlr = new ResolveEventHandler(assemblyResolve.AssemblyResolver);
AppDomain dom = Thread.GetDomain();
dom.AssemblyResolve += hndlr;
// Attempt to load the assembly. This should trigger the
// handler when the assembly is not found on disk.
// Load the assembly HelloWorld
Assembly asm = Assembly.Load("DynamicHelloWorld");
if (asm == null) {
Console.WriteLine("Main: Can't load assembly HelloWorld");
return;
}
// Lookup the type in the loaded assembly
Type t = asm.GetType("HelloWorld");
if (t == null) {
Console.WriteLine("Main: Can't find type HelloWorld");
return;
}
// Instantiate the type HelloWorld
Object o = Activator.CreateInstance(t, null);
// Use Reflection, to invoke the "SayHello" method
t.InvokeMember("SayHello", BindingFlags.Public | BindingFlags.Instance | BindingFlags.InvokeMethod, null, o,
null);
}
// The handler uses Reflection Emit to dynamically build
// the "DynamicHelloWorld" assembly with the type "HelloWorld"
public Assembly AssemblyResolver(Object sender, ResolveEventArgs args)
{
// Write message that we are in the assembly resolver
Console.WriteLine("AssemblyResolver: Building assembly" + args.Name + "...");
// Define the dynamic assembly
AssemblyName asmName = new AssemblyName();
asmName.Name = "DynamicHelloWorld";
AssemblyBuilder asm = Thread.GetDomain().DefineDynamicAssembly(asmName,
AssemblyBuilderAccess.Run);
// Define a dynamic module in the assembly
ModuleBuilder mod = asm.DefineDynamicModule("DynamicHelloWorld");
// Define the "HelloWorld" type in the module
TypeBuilder typ = mod.DefineType("HelloWorld", TypeAttributes.Public);
// Define the "SayHello" method
MethodBuilder meth = typ.DefineMethod("SayHello", MethodAttributes.Public, null, null);
ILGenerator il = meth.GetILGenerator();
il.EmitWriteLine("Hello World!");
il.Emit(OpCodes.Ret);
// Complete the type and return the dynamic assembly
typ.CreateType();
Console.WriteLine("Returning dynamic assembly");
return asm;
}
}
Compile AssemblyResolve.cs as follows:
csc AssemblyResolve.cs
A type is resolved dynamically by defining a handler for the TypeResolve event. The TypeResolve event is defined as
follows:
public event ResolveEventHandler TypeResolve
A resource is resolved dynamically by defining a handler for the ResourceResolve event. The ResourceResolve event is
defined as follows:
public event ResolveEventHandler ResourceResolve
For both types and resources, the handler must resolve the assembly in which the entity is defined. The code for the
handler is very similar to the handler shown in the sample above.
How do I unload an assembly?
CLR does not provide a way to unload an assembly. The only mechanism to remove the assembly is to unload the
application domain in which the assembly is loaded. If you wish to remove an assembly after it has been used, you
should create an application domain, load the assembly into the created application domain, and then unload the
application domain when you no longer need the assembly.
How do I unload an application domain?
You should use the following static method in the System.AppDomain class:
public static void Unload(AppDomain domain)
The Unload method gracefully shuts down the specified application domain. During shutdown no new threads are
allowed to enter the application domain and all application domain specific data structures are freed. You cannot
unload an application domain in a finalizer or destructor.
If the application domain has run code from a domain-neutral assembly, the domains copy of the statics and related
CLR data structures are freed, but the code for the domain-neutral assembly remains until the process is shutdown.
There is no mechanism to fully unload a domain-neutral assembly other than shutting down the process.
SQL SERVER 2000
1. What is normalization? - Well a relational database is basically composed of tables that contain related data.
So the Process of organizing this data into tables is actually referred to as normalization.
2. What is a Stored Procedure? - Its nothing but a set of T-SQL statements combined to perform a single task of
several tasks. Its basically like a Macro so when you invoke the Stored procedure, you actually run a set of statements.
3. Can you give an example of Stored Procedure? - sp_helpdb , sp_who2, sp_renamedb are a set of system
defined stored procedures. We can also have user defined stored procedures which can be called in similar way.
4. What is a trigger? - Triggers are basically used to implement business rules. Triggers is also similar to stored
procedures. The difference is that it can be activated when data is added or edited or deleted from a table in a
database.
5. What is a view? - If we have several tables in a db and we want to view only specific columns from specific
tables we can go for views. It would also suffice the needs of security some times allowing specfic users to see only
specific columns based on the permission that we can configure on the view. Views also reduce the effort that is
required for writing queries to access specific columns every time.
6. What is an Index? - When queries are run against a db, an index on that db basically helps in the way the data
is sorted to process the query for faster and data retrievals are much faster when we have an index.
7. What are the types of indexes available with SQL Server? - There are basically two types of indexes that we
use with the SQL Server. Clustered and the Non-Clustered.
8. What is the basic difference between clustered and a non-clustered index? - The difference is that, Clustered
index is unique for any given table and we can have only one clustered index on a table. The leaf level of a clustered
index is the actual data and the data is resorted in case of clustered index. Whereas in case of non-clustered index the
leaf level is actually a pointer to the data in rows so we can have as many non-clustered indexes as we can on the db.
9. What are cursors? - Well cursors help us to do an operation on a set of data that we retreive by commands
such as Select columns from table. For example : If we have duplicate records in a table we can remove it by declaring
a cursor which would check the records during retreival one by one and remove rows which have duplicate values.
10. When do we use the UPDATE_STATISTICS command? - This command is basically used when we do a large
processing of data. If we do a large amount of deletions any modification or Bulk Copy into the tables, we need to
basically update the indexes to take these changes into account. UPDATE_STATISTICS updates the indexes on these
tables accordingly.
11. Which TCP/IP port does SQL Server run on? - SQL Server runs on port 1433 but we can also change it for
better security.
12. From where can you change the default port? - From the Network Utility TCP/IP properties > Port
number.both on client and the server.
13. Can you tell me the difference between DELETE & TRUNCATE commands? - Delete command removes the
rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the
rows from a table and there will be no data in the table after we run the truncate command.
14. Can we use Truncate command on a table which is referenced by FOREIGN KEY? - No. We cannot use
Truncate command on a table with Foreign Key because of referential integrity.
15. What is the use of DBCC commands? - DBCC stands for database consistency checker. We use these
commands to check the consistency of the databases, i.e., maintenance, validation task and status checks.
16. Can you give me some DBCC command options?(Database consistency check) - DBCC CHECKDB - Ensures
that tables in the db and the indexes are correctly linked.and DBCC CHECKALLOC - To check that all pages in a db are
correctly allocated. DBCC SQLPERF - It gives report on current usage of transaction log in percentage. DBCC
CHECKFILEGROUP - Checks all tables file group for any damage.
17. What command do we use to rename a db? - sp_renamedb oldname , newname
18. Well sometimes sp_reanmedb may not work you know because if some one is using the db it will not accept
this command so what do you think you can do in such cases? - In such cases we can first bring to db to single user
using sp_dboptions and then we can rename that db and then we can rerun the sp_dboptions command to remove the
single user mode.
19. What is the difference between a HAVING CLAUSE and a WHERE CLAUSE? - Having Clause is basically used
only with the GROUP BY function in a query. WHERE Clause is applied to each row before they are part of the GROUP
BY function in a query.
20. What do you mean by COLLATION? - Collation is basically the sort order. There are three types of sort order
Dictionary case sensitive, Dictonary - case insensitive and Binary.
21. What is a Join in SQL Server? - Join actually puts data from two or more tables into a single result set.
22. Can you explain the types of Joins that we can have with Sql Server? - There are three types of joins: Inner
Join, Outer Join, Cross Join
23. When do you use SQL Profiler? - SQL Profiler utility allows us to basically track connections to the SQL Server
and also determine activities such as which SQL Scripts are running, failed jobs etc..
24. What is a Linked Server? - Linked Servers is a concept in SQL Server by which we can add other SQL Server to
a Group and query both the SQL Server dbs using T-SQL Statements.
25. Can you link only other SQL Servers or any database servers such as Oracle? - We can link any server
provided we have the OLE-DB provider from Microsoft to allow a link. For Oracle we have a OLE-DB provider for oracle
that microsoft provides to add it as a linked server to the sql server group.
26. Which stored procedure will you be running to add a linked server? - sp_addlinkedserver, sp_addlinkedsrvlogin
27. What are the OS services that the SQL Server installation adds? - MS SQL SERVER SERVICE, SQL AGENT
SERVICE, DTC (Distribution transac co-ordinator)
28. Can you explain the role of each service? - SQL SERVER - is for running the databases SQL AGENT - is for
automation such as Jobs, DB Maintanance, Backups DTC - Is for linking and connecting to other SQL Servers
29. How do you troubleshoot SQL Server if its running very slow? - First check the processor and memory usage
to see that processor is not above 80% utilization and memory not above 40-45% utilization then check the disk
utilization using Performance Monitor, Secondly, use SQL Profiler to check for the users and current SQL activities and
jobs running which might be a problem. Third would be to run UPDATE_STATISTICS command to update the indexes
30. Lets say due to N/W or Security issues client is not able to connect to server or vice versa. How do you
troubleshoot? - First I will look to ensure that port settings are proper on server and client Network utility for
connections. ODBC is properly configured at client end for connection Makepipe & readpipe are utilities to check for
connection. Makepipe is run on Server and readpipe on client to check for any connection issues.
31. What are the authentication modes in SQL Server? - Windows mode and mixed mode (SQL & Windows).
32. Where do you think the users names and passwords will be stored in sql server? - They get stored in master
db in the sysxlogins table.
33. What is log shipping? Can we do logshipping with SQL Server 7.0 - Logshipping is a new feature of SQL Server
2000. We should have two SQL Server - Enterprise Editions. From Enterprise Manager we can configure the
logshipping. In logshipping the transactional log file from one server is automatically updated into the backup database
on the other server. If one server fails, the other server will have the same db and we can use this as the DR (disaster
recovery) plan.
34. Let us say the SQL Server crashed and you are rebuilding the databases including the master database what
procedure to you follow? - For restoring the master db we have to stop the SQL Server first and then from command
line we can type SQLSERVER m which will basically bring it into the maintenance mode after which we can restore the
master db.
35. Let us say master db itself has no backup. Now you have to rebuild the db so what kind of action do you take?
- (I am not sure- but I think we have a command to do it).
36. What is BCP? When do we use it? - BulkCopy is a tool used to copy huge amount of data from tables and
views. But it wont copy the structures of the same.
37. What should we do to copy the tables, schema and views from one SQL Server to another? - We have to write
some DTS packages for it.
38. What are the different types of joins and what dies each do?
39. What are the four main query statements?
40. What is a sub-query? When would you use one?
41. What is a NOLOCK?
42. What are three SQL keywords used to change or set someones permissions?
43. What is the difference between HAVING clause and the WHERE clause?
44. What is referential integrity? What are the advantages of it?
45. What is database normalization?
46. Which command using Query Analyzer will give you the version of SQL server and operating system?
47. Using query analyzer, name 3 ways you can get an accurate count of the number of records in a table?
48. What is the purpose of using COLLATE in a query?
49. What is a trigger?
50. What is one of the first things you would do to increase performance of a query? For example, a boss tells you
that a query that ran yesterday took 30 seconds, but today it takes 6 minutes
51. What is an execution plan? When would you use it? How would you view the execution plan?
52. What is the STUFF function and how does it differ from the REPLACE function?
53. What does it mean to have quoted_identifier on? What are the implications of having it off?
54. What are the different types of replication? How are they used?
55. What is the difference between a local and a global variable?
56. What is the difference between a Local temporary table and a Global temporary table? How is each one used?
57. What are cursors? Name four types of cursors and when each one would be applied?
58. What is the purpose of UPDATE STATISTICS?
59. How do you use DBCC statements to monitor various aspects of a SQL server installation?
60. How do you load large data to the SQL server database?
61. How do you check the performance of a query and how do you optimize it?
62. How do SQL server 2000 and XML linked? Can XML be used to access data?
63. What is SQL server agent?
64. What is referential integrity and how is it achieved?
65. What is indexing?
66. What is normalization and what are the different forms of normalizations?
67. Difference between server.transfer and server.execute method?
68. What id de-normalization and when do you do it?
69. What is better - 2nd Normal form or 3rd normal form? Why?
70. Can we rewrite subqueries into simple select statements or with joins? Example?
71. What is a function? Give some example?
72. What is a stored procedure?
73. Difference between Function and Procedure-in general?
74. Difference between Function and Stored Procedure?
75. Can a stored procedure call another stored procedure. If yes what level and can it be controlled?
76. Can a stored procedure call itself(recursive). If yes what level and can it be controlled.?
77. How do you find the number of rows in a table?
78. Difference between Cluster and Non-cluster index?
79. What is a table called, if it does not have neither Cluster nor Non-cluster Index?
80. Explain DBMS, RDBMS?
81. Explain basic SQL queries with SELECT from where Order By, Group By-Having?
82. Explain the basic concepts of SQL server architecture?
83. Explain couple pf features of SQL server
84. Scalability, Availability, Integration with internet, etc.)?
85. Explain fundamentals of Data ware housing & OLAP?
86. Explain the new features of SQL server 2000?
87. How do we upgrade from SQL Server 6.5 to 7.0 and 7.0 to 2000?
88. What is data integrity? Explain constraints?
89. Explain some DBCC commands?
90. Explain sp_configure commands, set commands?
91. Explain what are db_options used for?
92. What is the basic functions for master, msdb, tempdb databases?
93. What is a job?
94. What are tasks?
95. What are primary keys and foreign keys?
96. How would you Update the rows which are divisible by 10, given a set of numbers in column?
97. If a stored procedure is taking a table data type, how it looks?
98. How m-m relationships are implemented?
99. How do you know which index a table is using?
100. How will oyu test the stored procedure taking two parameters namely first name and last name returning full
name?
101. How do you find the error, how can you know the number of rows effected by last SQL statement?
102. How can you get @@error and @@rowcount at the same time?
103. What are sub-queries? Give example? In which case sub-queries are not feasible?
104. What are the type of joins? When do we use Outer and Self joins?
105. Which virtual table does a trigger use?
106. How do you measure the performance of a stored procedure?
107. Questions regarding Raiseerror?
108. Questions on identity?
109. If there is failure during updation of certain rows, what will be the state?
What is normalization?
Normalization is the process of designing a data model to efficiently store data in a database. The end result is that
redundant data is eliminated, and only data related to the attribute is stored within the table.
For example, let's say we store City, State and ZipCode data for Customers in the same table as Other Customer data.
With this approach, we keep repeating the City, State and ZipCode data for all Customers in the same area. Instead of
storing the same data again and again, we could normalize the data and create a related table called City. The "City"
table could then store City, State and ZipCode along with IDs that relate back to the Customer table, and we can
eliminate those three columns from the Customer table and add the new ID column.
Normalization rules have been broken down into several forms. People often refer to the third normal form (3NF) when
talking about database design. This is what most database designers try to achieve: In the conceptual stages, data is
segmented and normalized as much as possible, but for practical purposes those segments are changed during the
evolution of the data model. Various normal forms may be introduced for different parts of the data model to handle
the unique situations you may face.
Whether you have heard about normalization or not, your database most likely follows some of the rules, unless all of
your data is stored in one giant table. We will take a look at the first three normal forms and the rules for determining
the different forms here.
Rules for First Normal Form (1NF)
Eliminate repeating groups. This table contains repeating groups of data in the Software column.
Computer Software
1 Word
2 Access, Word, Excel
3 Word, Excel
To follow the First Normal Form, we store one type of software for each record.
Computer Software
1 Word
2 Access
2 Word
3 Excel
3 Word
3 Excel
Rules for second Normal Form (2NF)
Eliminate redundant data plus 1NF. This table contains the name of the software which is redundant data.
Computer Software
1 Word
2 Access
2 Word
3 Excel
3 Word
3 Excel
To eliminate the redundant storage of data, we create two tables. The first table stores a reference SoftwareID to our
new table that has a unique list of software titles.
Computer SoftwareID
1 1
2 2
2 1
3 3
3 1
3 3
SoftwareID Software
1 Word
2 Access
3 Excel
Rules for Third Normal Form (3NF)
Eliminate columns not dependent on key plus 1NF and 2NF. In this table, we have data that contains both data about
the computer and the user.
Computer User Name User Hire Date Purchased
1 Joe 4/1/2000 5/1/2003
2 Mike 9/5/2003 6/15/2004
To eliminate columns not dependent on the key, we would create the following tables. Now the data stored in the
computer table is only related to the computer, and the data stored in the user table is only related to the user.
Computer Purchased
1 5/1/2003
2 6/15/2004
User User Name User Hire Date
1 Joe 5/1/2003
2 Mike 6/15/2004
Computer User
1 1
2 1
What does normalization have to do with SQL Server?
To be honest, the answer here is nothing. SQL Server, like any other RDBMS, couldn't care less whether your data
model follows any of the normal forms. You could create one table and store all of your data in one table or you can
create a lot of little, unrelated tables to store your data. SQL Server will support whatever you decide to do. The only
limiting factor you might face is the maximum number of columns SQL Server supports for a table.
SQL Server does not force or enforce any rules that require you to create a database in any of the normal forms. You
are able to mix and match any of the rules you need, but it is a good idea to try to normalize your database as much
as possible when you are designing it. People tend to spend a lot of time up front creating a normalized data model,
but as soon as new columns or tables need to be added, they forget about the initial effort that was devoted to
creating a nice clean model.
To assist in the design of your data model, you can use the DaVinci tools that are part of SQL Server Enterprise
Manager.
Advantages of normalization
1. Smaller database: By eliminating duplicate data, you will be able to reduce the overall size of the database.
2. Better performance:
a. Narrow tables: Having more fine-tuned tables allows your tables to have less columns and allows you to fit more
records per data page.
b. Fewer indexes per table mean faster maintenance tasks such as index rebuilds. c. Only join tables that you need.
Disadvantages of normalization
1. More tables to join: By spreading out your data into more tables, you increase the need to join tables.
2. Tables contain codes instead of real data: Repeated data is stored as codes rather than meaningful data. Therefore,
there is always a need to go to the lookup table for the value.
3. Data model is difficult to query against: The data model is optimized for applications, not for ad hoc querying.
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