Async exception not being caught or being swallowed

Question

Update from the future: TL;DR to catch expressions in async methods you have to await, Task.WaitAll, or .Result.

Answer 1

You can handle unobserved Task exceptions as follows:

TaskScheduler.UnobservedTaskException += (object sender, UnobservedTaskExceptionEventArgs eventArgs) =>
{
      eventArgs.SetObserved();
      ((AggregateException)eventArgs.Exception).Handle(ex =>
      {
          //TODO: inspect type and handle exception
          return true;
      });
};

Answer 2

When an async method throws an exception, that exception is placed on the returned Task. It's not raised directly to the caller. This is by design.

So, you have to either await the Task returned from LoadMSpecAsync or have your mSpecCompletionHandler examine its Task argument for exceptions. It will show up there.

Answer 3

I'm going to add an answer to my own question because there's a useful piece of information that I found out. The intermediary method LoadMSpecAsync is swalloing the exception. For this not to happen it needs a little teak. You need to add the async keyword before the return type and the "await" keyword after "return".