1) What is versioning?
2) What is DLL hell?
3) Destructor - It is called automatically when object is destroyed.
Rite or wrong?
4) Finalize or destructor are same?? They have same definitions.
5) Interfaces vs. Abstract Classes?
6) BCL vs FCL?

Let me preface this by saying that I've done some searching for you as they'll probably give better explanations that I will. If you have anymore questions after reading the links, then come back and we'll attempt to answer them.

Good luck in your interview!

1) Google search, select the first result.
2) Google search, select the first result.
3) Google search, select first result.
4) Not entirely sure, so I'm not going to provide links without knowing/understanding personally.
5) Google search, select the second result.
6) Google search, select the first result

1. That could be many things but likely they're talking about source control so you have a copy of the exact source code at each version
2. In the old days when you had a DLL named "file1.dll" that had to reside in C:\windows\system32\file1.dll you were screwed if Application A used v1.0, and Application B used v2.0 . It was DLL hell.
3. True
4. No they are not. A destructor implicitly calls the finalize method BUT you can implement more cleanup code in the destructor.
5. You can only inherit from a single class but you can implement any number of interfaces
6. no idea

[edit]
#4 -- Well actually I guess the ~Finalizer is interpreted at the MSIL level to Finalize() so in that respect they are the same. Its kind of an odd question. I would ask them to be more specific and explain the differences.
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