Catching an exception thrown in an asynchronous callback

Question

I have a method that takes a callback argument to execute asynchronously, but the catch block doesn\'t seem to be catching any exceptions thrown by the synchronous call (

Answer 1

If you're targeting .NET 4.0, you can utilize the new Task Parallel Library, and observe the Task object's Exception property.

public Task Submit(FileInfo file)
{
    return Task.Factory.StartNew(() => DoSomething(file));
}

private void DoSomething(FileInfo file)
{
    throw new Exception();
}

Then use it like this:

Submit(myFileInfo).ContinueWith(task =>
{
    // Check task.Exception for any exceptions.

    // Do stuff with task.Result
});

where DoSomething is the method you'd like call asynchronously, and the delegate you pass to ContinueWith is your callback.

More information about exception handling in TPL can be found here: http://msdn.microsoft.com/en-us/library/dd997415.aspx