Is there an equivalent of exit() for quitting a C# .NET application?

Is there a way to force garbage collection?

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().

Does C# support multiple-inheritance?

Who is a protected class-level variable available to?

It is available to any sub-class (a class inheriting this class).

Are private class-level variables inherited?

Yes, but they are not accessible.  Although they are not visible or accessible via the class interface, they are inherited.

Describe the accessibility modifier “protected internal”.

What does the term immutable mean?

The data value may not be changed.  Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.

What’s the difference between System.String and System.Text.StringBuilder classes?

What’s the advantage of using System.Text.StringBuilder over System.String?

StringBuilder is more efficient in cases where there is a large amount of string manipulation.  Strings are immutable, so each time a string is changed,  a new instance in memory is created.

What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?

The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array.  The CopyTo() method copies the elements into another existing array.  Both perform a shallow copy.  A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array.  A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.

Can multiple catch blocks be executed for a single try statement?

No.  Once the proper catch block processed, control is transferred to the finally block (if there are any).