Dot Net : Interview Question Part 2

1. What�s an interface class?
It�s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

2. Why can�t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it�s public by default.

3. Can you inherit multiple interfaces?
Yes

4. What�s the difference between an interface and abstract class?
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.

5. How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.

6. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

7. What�s the difference between System.String and System.StringBuilder classes?
System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

8. What�s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it�s being operated on, a new instance is created.

9. Can you store multiple data types in System.Array?
If the Array is System.Object Type then the answer is Yes else No.

10. What�s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The first one performs a deep copy of the array, the second one is shallow.

11. How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.

12. What�s the .NET datatype that allows the retrieval of data by a unique key?
HashTable.

13. What�s class SortedList underneath?
A sorted HashTable.

14. Will finally block get executed if the exception had not occurred?
Yes.

15. What�s the C# equivalent of C++ catch (�), which was a catch-all statement for any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.

16. Can multiple catch blocks be executed?
No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.

17. What�s a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.

18. What�s a multicast delegate?
It�s a delegate that points to and eventually fires off several methods.

19. How�s the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.

20. What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.

21. What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.

22. What�s the difference between // comments, /* */ comments and /// comments?
Single-line, multi-line and XML documentation comments.

23. How do you generate documentation from the C# file commented properly with a command-line compiler?
Compile it with a /doc switch.

24. What�s the difference between and XML documentation tag?
Single line code example and multiple-line code example.

25. Is XML case-sensitive?
Yes, so and are different elements.

26. What debugging tools come with the .NET SDK?
CorDBG � command-line debugger, and DbgCLR � graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.

27. What does assert() do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.

28. What�s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.

29. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.

30. Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.

31. How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.

32. What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).

33. Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.

34. Explain the three services model (three-tier application).
Presentation (UI), business (logic and underlying code) and data (from storage or other sources).

35. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it�s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.

36. What�s the role of the DataReader class in ADO.NET connections?
It returns a read-only dataset from the data source when the command is executed.

38. What does Dispose method do with the connection object?
Deletes it from the memory.

39. What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

40. Can you write a class without specifying namespace? Which namespace does it belong to by default??
Yes, then the class belongs to global namespace which has no name. For commercial products, naturally, you wouldn�t want global namespace.

41. What is Viewstate :
View state is used automatically by the ASP.NET page framework to persist information that must be preserved between postbacks. This information includes any non-default values of controls.
You can also use view state to store application data that is specific to a page.