Weird behavior with event returning Tasks not fully executing all subscribed methods

Question

I have the following event:

public static event Func<object, EventArgs, Task> Blocker;

I subscribe to it the following anonymous methods:

 Blocker += async (x, y) => { await Task.Delay(20); Console.WriteLine("Task1"); };
 Blocker += async (x, y) => { await Task.Delay(10); Console.WriteLine("Task2"); };
 Blocker += async (x, y) => { await Task.Delay(5000); Console.WriteLine("Task3"); };
 Blocker += async (x, y) => { await Task.Delay(1000); Console.WriteLine("Task4"); };

Now, if I invoke the event by writing await Blocker(null,null);, this returns before all of the subscribed methods have returned, yet if I go down the long path of executing them, by doing the following:

foreach (var item in Blocker.GetInvocationList())
{
    await ((Func<object, EventArgs, Task>)item)(null, null);
}

No such anomaly is seen.

What exactly is happening here? I thought under the hood, calling the event in turn uses a similar for-loop logic to go through the subscribed methods? I'm guessing it's due to the fact that the await keyword is working on the returned task of Blocker(null,null), and because that's an event, it gets confused and ends up doing the correct behavior, even though for me it looks wrong.

Only the last `Task` is returned and awaited, because it is a `MulticastDelegate`. I think you need a custom event like you say — Charlieface, Jan 22 '21 at 14:25
Check binki's comment in [this](https://stackoverflow.com/a/12451628/1672994) answer — user1672994, Jan 22 '21 at 14:33
You can also implement what has suggested in [this](https://stackoverflow.com/a/30739162/1672994) answer — user1672994, Jan 22 '21 at 14:38
Related: [How do I await events in C#?](https://stackoverflow.com/questions/27761852/how-do-i-await-events-in-c) — Theodor Zoulias, Jan 22 '21 at 14:57
@TheodorZoulias I know it's probably considered spam for me writing this, but you've helped me a great deal in the past. Thank you for continuing to do so! Async all the way! — SpiritBob, Jan 22 '21 at 15:21

Weird behavior with event returning Tasks not fully executing all subscribed methods

0 Answers0