Is there a situation in which Dispose won't be called for a 'using' block?

Question

This was a telephone interview question I had: Is there a time when Dispose will not be called on an object whose scope is declared by a using block?

My answer was no - even if an exception happens during the using block, Dispose will still be called.

The interviewer disagreed and said if using is wrapped in a try-catch block then Dispose will not be called by the time you enter the catch block.

This goes contrary to my understanding of the construct, and I haven't been able to find anything that backs up the interviewers point of view. Is he correct or might I have misunderstood the question?

Answer 1

Four things that will cause Dispose to not be called in a using block:

1. A power failure on your machine when inside the using block.
2. Your machine getting melted by an atomic bomb while in the inside of the using block.
3. Uncatchable exceptions like StackOverflowException, AccessViolationException and possibly others.
4. Environment.FailFast

Answer 2

void Main() {     try     {         using(var d = new MyDisposable())         {             throw new Exception("Hello");         }     }     catch     {         "Exception caught.".Dump();     }  }  class MyDisposable : IDisposable {     public void Dispose()     {         "Disposed".Dump();     } } 

This produced :

Disposed Exception caught 

So I agree with you and not with the smarty interviewer...