Using Tasks with conditional continuations

I think your main problem is that you’re telling those two tasks to “Wait” with your call to

Task.WaitAll(onSuccess, onError);

The onSuccess and onError continuations are automatically setup for you and will be executed after their antecedent task completes.

If you simply replace your Task.WaitAll(...) with taskThrows.Start(); I believe you will get the desired output.

Here is a bit of an example I put together:

class Program
{
    static int DivideBy(int divisor) 
    { 
      Thread.Sleep(2000);
      return 10 / divisor; 
    }

    static void Main(string[] args)
    {
        const int value = 0;

        var exceptionTask = new Task<int>(() => DivideBy(value));

        exceptionTask.ContinueWith(result => Console.WriteLine("Faulted ..."), TaskContinuationOptions.OnlyOnFaulted | TaskContinuationOptions.AttachedToParent);
        exceptionTask.ContinueWith(result => Console.WriteLine("Success ..."), TaskContinuationOptions.OnlyOnRanToCompletion | TaskContinuationOptions.AttachedToParent);

        exceptionTask.Start();

        try
        {
            exceptionTask.Wait();
        }
        catch (AggregateException ex)
        {
            Console.WriteLine("Exception: {0}", ex.InnerException.Message);
        }

        Console.WriteLine("Press <Enter> to continue ...");
        Console.ReadLine();
    }
}