1. 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.

2. Can you store multiple data types in System.Array?

No.

3. 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.

4. How can you sort the elements of the array in descending order?

By calling Sort() and then Reverse() methods.
 

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

6. What’s class SortedList underneath?

A sorted HashTable.
 

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

8. 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 {}.
 

9.  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.
 

10. Why is it a bad idea to throw your own exceptions?

Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
 

11.  What’s a delegate?

A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
 

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