Is it possible to continue with task C after A and B run to completion without fault or cancellation using a single TPL method?

I've tried to use Task.Factory.ContinueWhenAll() a few times now with the intent of invoking a continuation only when all the antecedents run to completion without any errors or cancellations. Doing so causes an ArgumentOutOfRangeException to be thrown with the 开发者_运维知识库message,

It is invalid to exclude specific continuation kinds for continuations off of multiple tasks. Parameter name: continuationOptions

For example, the code

var first = Task.Factory.StartNew<MyResult>(
    DoSomething,
    firstInfo,
    tokenSource.Token);
var second = Task.Factory.StartNew<MyResult>(
    DoSomethingElse,
    mystate,
    tokenSource.Token);
var third = Task.Factory.ContinueWhenAll(
    new[] { first, second },
    DoSomethingNowThatFirstAndSecondAreDone,
    tokenSource.Token,
    TaskContinuationOptions.OnlyOnRanToCompletion, // not allowed!
    TaskScheduler.FromCurrentSynchronizationContext());

is not acceptable to the TPL. Is there a way to do something like this using some other TPL method?

There doesn't appear to be a direct way to do this. I've gotten around this by changing OnlyOnRanToCompletion to None and checking to see if Exception is non-null for each task passed into the continuation. Something like

private void DoSomethingNowThatFirstAndSecondAreDone(Task<MyResult>[] requestTasks)
{
    if (requestTasks.Any(t => t.Exception != null))
        return;

    // otherwise proceed...
}

works, but this doesn't seem to be a very satisfying way to handle the case with multiple antecedents and breaks with the pattern the single-case Task.Factory.ContinueWith uses.