Task.cs

public static Task WhenAllOrFaulted(params Task[] tasks)
{
    var faultedContinuations = new Task[tasks.Length];

    var faultedTask = new TaskCompletionSource<Task>();

    for (int i = 0; i < tasks.Length; i++)
    {
        faultedContinuations[i] = tasks[i].ContinueWith(t => faultedTask.SetResult(t), TaskContinuationOptions.OnlyOnFaulted);
    }

    var successTask = Task.WhenAll(tasks);

    return Task.WhenAny(faultedTask.Task, successTask);
}