Task Cancellation and TaskContinuationOptions

Question

I was just introduced to Tasks (TPL) yesterday, and so I tried to do a little sample project in order to develop an understanding of how to use them.

My sample proje

Answer 1

The comments above are correct in terms of the debugger and the options required to prevent the debugger breaking. However, the following should give you a better example of how to use continuations and indeed how to handle exceptions thrown from tasks within those continuations...

A continuation can find out if an exception was thrown by the antecedent Task by the antecedent task's exception property. The following prints the results of a NullReferenceException to the console

Task task1 = Task.Factory.StartNew (() => { throw null; });
Task task2 = task1.ContinueWith (ant => Console.Write(ant.Exception());

If task1 throws an exception and this exception is not captured/queried by the continuation it is considered unhandled and the application dies. With continuations it is enough to establish the result of the task via the Status keyword

asyncTask.ContinueWith(task =>
{
    // Check task status.
    switch (task.Status)
    {
        // Handle any exceptions to prevent UnobservedTaskException.             
        case TaskStatus.RanToCompletion:
            if (asyncTask.Result)
            {
                // Do stuff...
            }
            break;
        case TaskStatus.Faulted:
            if (task.Exception != null)
                mainForm.progressRightLabelText = task.Exception.InnerException.Message;
            else
                mainForm.progressRightLabelText = "Operation failed!";
        default:
            break;
    }
}

If you don't use continuations you either have to wait on the task in a try/catch block or query a task's Result in a try/catch block

int x = 0;
Task task = Task.Factory.StartNew (() => 7 / x);
try
{
    task.Wait();
    // OR.
    int result = task.Result;
}
catch (AggregateException aggEx)
{
    Console.WriteLine(aggEx.InnerException.Message);
}

Hope this helps.