Is there default way to get first task that finished successfully?

Question

Lets say that i have a couple of tasks:

void Sample(IEnumerable someInts)
{
    var taskList = someInts.Select(x => DownloadSomeString(x));
}

         


        

Answer 1

Modified version of @Servy 's code because it contains some compile errors and several pitfalls. My variant is:

public static class AsyncExtensions
{
    public static Task GetFirstSuccessfulTask(this IReadOnlyCollection> tasks)
    {
        var tcs = new TaskCompletionSource();
        int remainingTasks = tasks.Count;
        foreach (var task in tasks)
        {
            task.ContinueWith(t =>
            {
                if (task.Status == TaskStatus.RanToCompletion)
                    tcs.TrySetResult(t.Result);
                else if (Interlocked.Decrement(ref remainingTasks) == 0)
                    tcs.SetException(new AggregateException(
                        tasks.SelectMany(t2 => t2.Exception?.InnerExceptions ?? Enumerable.Empty())));
            });
        }
        return tcs.Task;
    }
}

We don't have to ToList our input because it's already a collection we can work with, it compiles (huge advantage) and it handles situation when exception for some reason doesn't have an innter exception (it's completely possible).