Question

I have a Function executing Some piece of code Like,

Protected void XXXXfunc()
{
  //i register a callback for asynchronous operation below is just an example
  // not true to its operation 
  byte[] buffer = new byte[10];

  s.BeginReceive(buffer, 0, 10, SocketFlags.None,
      new AsyncCallback(OnMessageReceived), buffer);
}

// Callback function
XXXX callback OnMessageReceived(XXXX)
{
  //Something Goes wrong here i throw an exception 
  throw(exception);
}

Where and how do i catch this exception or where is this exception funneled to be caught.

Answer 1

In the callback, the only place you can catch it.

And yes, that’s a very awkward place because that callback runs on a thread you didn’t start and runs completely asynchronously from the rest of your code. You have to somehow let the main logic in your program know that something went wrong and that corrective action needs to be taken. Which typically requires raising an event that gets marshaled back to your main thread. At the very least to let the user know that “it didn’t work”.

This kind of problem is the prime motivation behind the Task<> class in C# version 4 and the async/await keywords added to C# version 5. Which doesn’t actually do anything to help the user deal with random failure, it just makes it easier to report.