Monday, August 25, 2008

.Net Interview Questions


1. Microsoft .NET Framework interview questions .NET

2. What is .NET Framework?

3. Is .NET a runtime service or a development platform? Answer It’s bothand actually a lot more. Microsoft .NET is a company-wide initiative. It includes a new way of delivering software and services to businesses and consumers. A part of Microsoft.NET is the .NET Frameworks. The frameworks is the first part of the MS.NET initiate to ship and it was given out to attendees at the PDC in July. The .NET frameworks consists of two parts: the .NET common language runtime and the .NET class library. These two components are packaged together into the .NET Frameworks SDK which will be available for free download from Microsoft’s MSDN web site later this month. 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. When Visual Studio.NET ships, it will include the .NET SDK and a GUI editor, wizards, tools, and a slew of other things. However, Visual Studio.NET is NOT required to build .NET applications.

4. New features of Framework 1.1 ?

5. What is CLR? How it will work?

6. What is MSIL, IL, CTS?

7. What is JIT and how is works

8. What is strong name? A name that consists of an assembly’s identity—its simple text name, version number, and culture information (if provided)—strengthened by a public key and a digital signature generated over the assembly.

9. 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

10. Which is the base class for .net Class library? Ans: system.object

11. What is Event? Delegate, clear syntax for writing a event delegate// 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)

public static void DelegateFunction(int i)
System.Console.WriteLine("Called by delegate withnumber: {0}.", i);


12. ment DataGrid in .NET? How would you 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?

13. If we write any code for DataGrid methods, what is the access specifier used for that methods in the code behind file and why?

14. What is Application Domain? Application domains provide a unit of isolation for the common language runtime. They are created and run inside a process. Application domains are usually created by a runtime host, which is an application responsible for loading the runtime into a process and executing user code within an application domain. The runtime host creates a process and a default application domain, and runs managed code inside it. Runtime hosts include ASP.NET, Microsoft Internet Explorer, and the Windows shell.

15. What is serialization in .NET? What are the ways to control serialization? 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.

a. 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.

b. 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.

16. What are the different authentication modes in the .NET environment?

17. What is the use of trace utility

18. What is different between User Control and Web Control and Custom Control?

19. 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 withtry statements more nested that than the one that caught the exception. Exceptions that occur during destructor execution are worthspecial 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.

20. 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 withthe 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 withthe .NET Framework. An assembly performs the following functions:

a. 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, orMain).

b. It forms asecurity boundary. An assembly is the unit at which permissions are requested and granted.

c. It forms atype 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.

d. It forms areference 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.

e. It forms aversion 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.

f. 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.

g. 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.

i. 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 withmodules created in other development environments. You can also use common language runtime APIs, such as Reflection.Emit, to create dynamic assemblies.

21. s of assemblies? Private, Public/Shared, Satellite

22. 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 witha 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 withlocalized 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.

23. How will you load dynamic assembly? How will create assemblies at run time?

24. 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) withMicrosoft 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.

25. What are the contents of assembly? In general, a static assembly can consist of four elements:

a. The assembly manifest, which contains assembly metadata.

b. Type metadata.

c. Microsoft intermediate language (MSIL) code that implements the types.

d. A set of resources.

26. 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.

27. What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to public? Steps) 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.

28. 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?

29. How to find methods of a assembly file (not using ILDASM) Reflection

30. Value type & data types difference. Example from .NET.

31. Integer & struct are value types or reference types in .NET?

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? Aconstfield can only be initialized at the declaration of the field. Areadonlyfield can be initialized either at the declaration or in a constructor. Therefore,readonlyfields can have different values depending on the constructor used. Also, while aconstfield is a compile-time constant, thereadonlyfield can be used for runtime constants, as in the following example: public static readonly uint l1 = (uint) DateTime.Now.Ticks;

< . { System.Attribute : MyAttribute public attribute.(>

< { public this.myvalue="myvalue;" myvalue) MyAttribute(bool constructors(>

//Declaring properties
public bool MyProperty
get {return this.myvalue;}
set {this.myvalue = value;}
ion 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 ++)

34. C++ & C# differences

35. 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 witha language compiler that targets the runtime is calledmanaged code; itbenefits 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.

36. How do you create threading in .NET? What is the namespace for that?

37. using directive vs using statement You create an instance in ausingstatement to ensure thatDispose is called on the object when theusingstatement is exited. Ausing statement can be exited either when the end of theusingstatement 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.

a. Create an alias for a namespace (a using alias).

b. Permit the use of types in a namespace, such that, you do not have to qualify the use of a type in that namespace (ausingdirective).

38. Describe the Managed Execution Process

39. What is Active Directory? What is the namespace used to access the Microsoft Active Directories?

40. Interop Services?

41. What is RCW (Run time 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.

42. What is CCW (COM Callable Wrapper)

43. A proxy object generated by the common language runtime so that existing COM applications can use managed classes, including .NET Framework classes, transparently.

44. How does you handle this COM components developed in other programming languages in .NET?

45. How will you register com+ services?

46. What is use of ContextUtil class? ContextUtil is the preferred class to use for obtaining COM+ context information.

47. What is the new three features of COM+ services, which are not there in COM (MTS)

48. Is the COM architecture same as .Net architecture? What is the difference between them (if at all there is)?

49. How big is the datatype int in .NET? 32 bits.

50. How big is the char? 16 bits (Unicode).

51. How do you initiate a string without escaping each backslash? Put an @ sign in front of the double-quoted string.

52. What are valid signatures for the Main function?

a. public static void Main()

b. public static int Main()

c. public static void Main( string[] args )

d. public static int Main(string[] args )

53. Does Main() always have to be public? No.

54. How do you initialize a two-dimensional array that you don’t know the dimensions of?

a. int [, ] myArray; //declaration

b. myArray= new int [5, 8]; //actual initialization

55. What’s the access level of the visibility type internal? Current assembly.

56. What’s the difference between struct and class in C#?

a. Structs cannot be inherited.

b. Structs are passed by value, not by reference.

c. Struct is stored on the stack, not the heap.

57. Explain encapsulation. The implementation is hidden, the interface is exposed.

58. What data type should you use if you want an 8-bit value that’s signed? sbyte.

59. Speaking of Boolean data types, what’s different between C# and C/C++? There’s no conversion between 0 and false, as well as any other number and true, like in C/C++.

60. Where are the value-type variables allocated in the computer RAM? Stack.

61. Where do the reference-type variables go in the RAM? The references go on the stack, while the objects themselves go on the heap. However, in reality things are more elaborate.

62. What is the difference between the value-type variables and reference-type variables in terms of garbage collection? The value-type variables are not garbage-collected, they just fall off the stack when they fall out of scope, the reference-type objects are picked up by GC when their references go null.

63. How do you convert a string into an integer in .NET? Int32.Parse(string), Convert.ToInt32()

64. How do you box a primitive data type variable? Initialize an object with its value, pass an object, cast it to an object

65. Why do you need to box a primitive variable? To pass it by reference or apply a method that an object supports, but primitive doesn’t.

66. What’s the difference between Java and .NET garbage collectors? Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.

67. How do you enforce garbage collection in .NET? System.GC.Collect();

68. Can you declare a C++ type destructor in C# like ~MyClass()? Yes, but what’s the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up, plus, it introduces additional load on the garbage collector. The only time the finalizer should be implemented, is when you’re dealing with unmanaged code.

69. What’s different about namespace declaration when comparing that to package declaration in Java? No semicolon. Package declarations also have to be the first thing within the file, can’t be nested, and affect all classes within the file.

70. What’s the difference between const and readonly? You can initialize readonly variables to some runtime values. Let’s say your program uses current date and time as one of the values that won’t change. This way you declare

i. public readonly string DateT = new DateTime().ToString().

71. Can you create enumerated data types in C#? Yes.

72. What’s different about switch statements in C# as compared to C++? No fall-throughs allowed.

73. What happens when you encounter a continue statement inside the for loop? The code for the rest of the loop is ignored, the control is transferred back to the beginning of the loop.

74. 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.

75. Describe the compilation process for .NET code? Source code is compiled and run in the .NET Framework using a two-stage process. First, source code is compiled to Microsoft intermediate language (MSIL) code using a .NET Framework-compatible compiler, such as that for Visual Basic .NET or Visual C#. Second, MSIL code is compiled to native code.

76. Name any 2 of the 4 .NET authentification methods. ASP.NET, in conjunction with Microsoft Internet Information Services (IIS), can authenticate user credentials such as names and passwords using any of the following authentication methods:

a. Windows: Basic, digest, or Integrated Windows Authentication (NTLM or Kerberos).

b. Microsoft Passport authentication

c. Forms authentication

d. Client Certificate authentication

77. How do you turn off SessionState in the web.config file? In the system.web section of web.config, you should locate the httpmodule tag and you simply disable session by doing a remove tag with attribute name set to session.

78. What is main difference between Global.asax and Web.Config? ASP.NET uses the global.asax to establish any global objects that your Web application uses. The .asax extension denotes an application file rather than .aspx for a page file. Each ASP.NET application can contain at most one global.asax file. The file is compiled on the first page hit to your Web application. ASP.NET is also configured so that any attempts to browse to the global.asax page directly are rejected. However, you can specify application-wide settings in the web.config file. The web.config is an XML-formatted text file that resides in the Web site’s root directory. Through Web.config you can specify settings like custom 404 error pages, authentication and authorization settings for the Web site, compilation options for the ASP.NET Web pages, if tracing should be enabled, etc.

79. Questions mainly relate to drawing and graphics programming in Windows Forms, when programming C# under .NET

I am constantly writing the drawing procedures with System.Drawing.Graphics, but having to use the try and dispose blocks is too time-consuming with Graphics objects. Can I automate this? Yes, the code

System.Drawing.Graphics canvas = new System.Drawing.Graphics();

//some code

is functionally equivalent to

using (System.Drawing.Graphics canvas = new System.Drawing.Graphics())


//some code

} //canvas.Dispose() gets called automatically

81. How do you trigger the Paint event in System.Drawing?Invalidate the current form, the OS will take care of repainting. The Update method forces the repaint.

82. With these events, why wouldn’t Microsoft combine Invalidate and Paint, so that you wouldn’t have to tell it to repaint, and then to force it to repaint? Painting is the slowest thing the OS does, so usually telling it to repaint, but not forcing it allows for the process to take place in the background.

83. How can you assign an RGB color to a System.Drawing.Color object? Call the static method FromArgb of this class and pass it the RGB values.

84. What class does Icon derive from? Isn’t it just a Bitmap with a wrapper name around it? No, Icon lives in System.Drawing namespace. It’s not a Bitmap by default, and is treated separately by .NET. However, you can use ToBitmap method to get a valid Bitmap object from a valid Icon object.

85. Before in my VB app I would just load the icons from DLL. How can I load the icons provided by .NET dynamically? By using System.Drawing.SystemIcons class, for example System.Drawing.SystemIcons.Warning produces an Icon with a warning sign in it.

86. When displaying fonts, what’s the difference between pixels, points and ems? A pixel is the lowest-resolution dot the computer monitor supports. Its size depends on user’s settings and monitor size. A point is always 1/72 of an inch. An em is the number of pixels that it takes to display the letter M.

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