C# quations - answers

Good for preparation and general self-testing, but too specific for the actual job interview. This was sent in by a job applicant getting ready to step into the .NET field in India.

1. Are private class-level variables inherited? - Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
2. Why does DllImport not work for me? - All methods marked with the DllImport attribute must be marked as public static extern.
3. Why does my Windows application pop up a console window every time I run it? - Make sure that the target type set in the project properties setting is set to Windows Application, and not Console Application. If you’re using the command line, compile with /target:winexe, not /target:exe.
4. Why do I get an error (CS1006) when trying to declare a method without specifying a return type? - If you leave off the return type on a method declaration, the compiler thinks you are trying to declare a constructor. So if you are trying to declare a method that returns nothing, use void. The following is an example: // This results in a CS1006 error public static staticMethod (mainStatic obj) // This will work as wanted public static void staticMethod (mainStatic obj)
5. Why do I get a syntax error when trying to declare a variable called checked? - The word checked is a keyword in C#.
6. Why do I get a security exception when I try to run my C# app? - Some security exceptions are thrown if you are working on a network share. There are some parts of the frameworks that will not run if being run off a share (roaming profile, mapped drives, etc.). To see if this is what’s happening, just move the executable over to your local drive and see if it runs without the exceptions. One of the common exceptions thrown under these conditions is System.Security.SecurityException. To get around this, you can change your security policy for the intranet zone, code group 1.2, (the zone that running off shared folders falls into) by using the caspol.exe tool.
7. Why do I get a CS5001: does not have an entry point defined error when compiling? - The most common problem is that you used a lowercase ‘m’ when defining the Main method. The correct way to implement the entry point is as follows: class test { static void Main(string[] args) {} }
8. What optimizations does the C# compiler perform when you use the /optimize+ compiler option? - The following is a response from a developer on the C# compiler team: We get rid of unused locals (i.e., locals that are never read, even if assigned). We get rid of unreachable code. We get rid of try-catch with an empty try. We get rid of try-finally with an empty try. We get rid of try-finally with an empty finally. We optimize branches over branches: gotoif A, lab1 goto lab2: lab1: turns into: gotoif !A, lab2 lab1: We optimize branches to ret, branches to next instruction, and branches to branches.
9. What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)? - The syntax for calling another constructor is as follows: class B { B(int i) { } } class C : B { C() : base(5) // call base constructor B(5) { } C(int i) : this() // call C() { } public static void Main() {} }
10. What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development? - Try using RegAsm.exe. Search MSDN on Assembly Registration Tool.
11. What is the difference between a struct and a class in C#? - From language spec: The list of similarities between classes and structs is as follows. Longstructs can implement interfaces and can have the same kinds of members as classes. Structs differ from classes in several important ways; however, structs are value types rather than reference types, and inheritance is not supported for structs. Struct values are stored on the stack or in-line. Careful programmers can sometimes enhance performance through judicious use of structs. For example, the use of a struct rather than a class for a Point can make a large difference in the number of memory allocations performed at runtime. The program below creates and initializes an array of 100 points. With Point implemented as a class, 101 separate objects are instantiated-one for the array and one each for the 100 elements.
12. My switch statement works differently than in C++! Why? - C# does not support an explicit fall through for case blocks. The following code is not legal and will not compile in C#:

13.       switch(x)

14.       {

15.               case 0: // do something

16.               case 1: // do something as continuation of case 0

17.               default: // do something in common with

18.                      //0, 1 and everything else

19.               break;

20.       }

To achieve the same effect in C#, the code must be modified as shown below (notice how the control flows are explicit):

class Test

{

  public static void Main() {

         int x = 3;

         switch(x)

         {

                 case 0: // do something

                 goto case 1;

                 case 1: // do something in common with 0

                 goto default;

                 default: // do something in common with 0, 1, and anything else

                 break;

         }

  }

}

21. Is there regular expression (regex) support available to C# developers? - Yes. The .NET class libraries provide support for regular expressions. Look at the System.Text.RegularExpressions namespace.
22. Is there any sample C# code for simple threading? - Yes:

23.       using System;

24.       using System.Threading;

25.       class ThreadTest

26.       {

27.               public void runme()

28.               {

29.                      Console.WriteLine("Runme Called");

30.               }

31.               public static void Main(String[] args)

32.               {

33.                      ThreadTest b = new ThreadTest();

34.                      Thread t = new Thread(new ThreadStart(b.runme));

35.                      t.Start();

36.               }

}

37. Is there an equivalent of exit() for quitting a C# .NET application? - Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it’s a Windows Forms app.
38. Is there a way to force garbage collection? - Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn’t seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
39. Is there a way of specifying which block or loop to break out of when working with nested loops? - The easiest way is to use goto:

40.       using System;

41.       class BreakExample

42.       {

43.               public static void Main(String[] args) {

44.                      for(int i=0; i<3;>

45.                      {

46.                              Console.WriteLine(”Pass {0}: “, i);

47.                              for( int j=0 ; j<100>

48.                              {

49.                                      if ( j == 10)

50.                                             goto done;

51.                                      Console.WriteLine(”{0} “, j);

52.                              }

53.                              Console.WriteLine(”This will not print”);

54.                      }

55.                      done:

56.                              Console.WriteLine(”Loops complete.”);

57.               }

}

58. Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace? - There is no way to restrict to a namespace. Namespaces are never units of protection. But if you’re using assemblies, you can use the ‘internal’ access modifier to restrict access to only within the assembly.

.Net & C# Interview question, along with general programming questions

Hey, These are some Interview Questions with suggested answers we collected in Middle-East-Developers, for more questions in other fields like C++, you can check the group.
These questions are collected by

• Adel Khalil
• Yehia Megahed
• Hisham Abd El-Hafez
• Mohammed Hossam

Q1: Can DateTime variables be null?
A1: No, because it is a value type (Struct)

Q2: Describe the Asp.net Page Life Cycle?
A2: http://msdn2.microsoft.com/en-us/library/ms178472.aspx

Q3: Describe the Asp.net pipeline ? Give an Example when you need to extend it? How do you do so?
A3: http://msdn.microsoft.com/msdnmag/issues/02/09/HTTPPipelines/

Q4: Describe the accessibility modifier protected internal
A4: Members are accessible to derived classes and classes within the same Assembly

Q5: Difference between an interface and abstract class?
A5: In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

Q6: How do you perform pre- and post-processing to extend a WebMethod ?
A6: Use SOAP extensions ...http://msdn.microsoft.com/msdnmag/issues/04/03/ASPColumn/

Q7: What are Design Patterns?
A7: It is a big topic in Object Oriented, so for more information see this, http://dofactory.com/Patterns/Patterns.aspx

Q8: What do you know about .net framework 3.0 ?
A8: any answer that introduces Windows Communication Foundation (WCF), Windows Workflow Foundation (WF), Windows Presentation Foundation (WPF) and Windows Card Space (WCS) is right, also you can mention that it was originally called WinFX

Q9: What do you know about ATLAS (Microsoft ASP.net AJAX Extensions) ?
A9: for more information check here, http://ajax.asp.net

Q10: What do you know about Agile software methodologies?
A10: http://en.wikipedia.org/wiki/Agile_software_development

Q11: What do you know about Web Services Enhancements (WSE)?
A11: http://msdn.microsoft.com/webservices/webservices/building/wse/default.aspx

Q12: What is AJAX ?
A12: Asynchronous Javascript And XML

Q13:What is NUnit, or What is Unit testing?
A13: Unit testing: is a procedure used to validate that a particular module of source code is working properly from each modification to the next. The procedure is to write test cases for all functions and methods so that whenever a change causes a regression, it can be quickly identified and fixed. Ideally, each test case is separate from the others; constructs such as mock objects can assist in separating unit tests. This type of testing is mostly done by the developers, NUnit is a famous tool for Unit Testing in .net

Q14: What is an Asp.net Http Handler & Http Module?
A14: http://www.15seconds.com/issue/020417.htm

Q15: What is mutable type ? immutable type ?
A15: Immutable type are types whose instance data, fields and properties, does not change after the instance is created. Most value types are immutable, but the mutable type are A type whose instance data, fields and properties, can be changed after the instance is created. Most Reference Types are mutable.

Q16: What is the HttpContext Object? Where is it accessible?
A16: It's is an Object that Encapsulates all HTTP-specific information about an individual HTTP request. it is avaliable through out the Asp.net request pipline.

Q17: What is the difference between String & StringBuilder classes?
A17: String is an immutable type while StringBuilder is a mutable type

Q18: What's the difference between C# 1.0 & C# 2.0?
A18: Any answer that introduces stuff like, Generics, Anonymous Methods, Nullable types, Iterators ... etc, is correct

Q19: Without using the multiplication or addition operations, how can you multiply a number x by 8?
A19: Shift x to the left 3 times, x <<>

Q20: What is the difference between ASP.net 1.x & ASP.net 2.0 ?
A20: Any answer that include stuff like Provider model (membership provider, role provider ... etc) and Master Pages, Code Beside model, new web controls will be ok.