How to make Task.WaitAll() to break if any exception happened?

Question

I want to make Task.WaitAll() to break out if any of the running tasks throws an exception, so that I don't have to wait for 60 seconds to finish. How do I achieve such behavior? If WaitAll() cannot achieve that, is there any other c# feature or workaround?

Task task1 = Task.Run(() => throw new InvalidOperationException()); Task task2 = ... ... try {     Task.WaitAll(new Task[]{task1, task2, ...}, TimeSpan.FromSeconds(60)); } catch (AggregateException) {     // If any exception thrown on any of the tasks, break out immediately instead of wait all the way to 60 seconds. } 

Answer 1

The following should do it without altering the code of the original tasks (untested):

static bool WaitAll(Task[] tasks, int timeout, CancellationToken token) {     var cts = CancellationTokenSource.CreateLinkedTokenSource(token);      var proxyTasks = tasks.Select(task =>          task.ContinueWith(t => {             if (t.IsFaulted) cts.Cancel();             return t;          },          cts.Token,          TaskContinuationOptions.ExecuteSynchronously,          TaskScheduler.Current).Unwrap());      return Task.WaitAll(proxyTasks.ToArray(), timeout, cts.Token); } 

Note it only tracks faulted tasks (those which threw). If you need to track cancelled tasks as well, make this change:

if (t.IsFaulted || t.IsCancelled) cts.Cancel(); 

Updated, waiting on the task proxies is redundant here, as pointed out by @svick in the comments. He proposes an improved version: https://gist.github.com/svick/9992598.