同时运行任务 .NET 4.5

Question

why does the method AwakeTest take 3 seconds instead of one

public static async void AwakeTest()
{
    var Do1 = Sleep(1, 1);
    var Do2 = Sleep(1, 2);
    var Do3 = Sleep(1, 3);

    await System.Threading.Tasks.Task.WhenAll(Do1, Do2, Do3); 

    Console.WriteLine(await Do1);
    Console.WriteLine(await Do2);
    Console.WriteLine(await Do3);
}

private static async System.Threading.Tasks.Task<int> Sleep(int Seconds, int ID)
{
    if (Seconds < 0)
    {
        throw new Exception();
    }
    System.Threading.Thread.Sleep(Seconds * 1000);
    return ID;
}

Answer 1

Since Thread.Sleep sleeps the thread, and each Task doesn't require to run in a separate thread, it hangs the entire thread.

You should use Task.Delay instead:

await Task.Delay(Seconds * 1000);