await still blocks current UI thread

Question

I tried to use the following code to run some task in thread pool:

private async void button1_Click(object sender, EventArgs e)
{
   await test().ConfigureAwait(continueOnCapturedContext: false);
}
private Task test()
{
   Thread.Sleep(100000);
   return null;
}

The code is supposed to run in the threadpool, however the current UI thread is still being blocked.

So can anyone help to take a look? thanks,

Using `async` / `await` does not mean that your task will run on a different thread. — dotnetom, Apr 12 '16 at 04:12
but should "continueOnCapturedContext: false" make it run in thread pool? — HPPPY, Apr 12 '16 at 04:16
No, `continueOnCapturedContext: false` will ensure that the continuation of an `await` is not invoked using the `SynchronizationContext` and instead finishes in `ThreadPool`. In your question your `Thread.Sleep()` is simply executed on the same thread that invoked the `test()` method, therefore it blocks. The code will run synchronously until it comes to the first `await`. So `test()` is invoked synchronously, the result (a `null` `Task`) is "awaited". — deloreyk, Apr 12 '16 at 05:02
Is your Test() method is `synchronized` or do it have `async` invocation ? — Eldho, Apr 12 '16 at 05:57
if its synchronized you could try using `await Task.Run(() =>Test());` — Eldho, Apr 12 '16 at 05:59
Your code is returning `null` instead of a `Task` that represents the asynchronous operation! — David Pine, Apr 12 '16 at 12:06

score 5 · Answer 1 · edited Jun 20 '20 at 09:12

The code is supposed to run in the threadpool

No, that is not at all true. async does not run your code on a thread pool thread.

I suggest you read my async intro, which explains what async does do, and the official async FAQ, which addresses the thread pool misconception specifically:

Does the “async” keyword cause the invocation of a method to queue to the ThreadPool? To create a new thread? To launch a rocket ship to Mars?

No. No. And no.

score 2 · Answer 2 · edited May 23 '17 at 12:24

2

You should use Task.Delay method.

private async void button1_Click(object sender, EventArgs e)
{
   await test();
}

private Task test()
{
    return Task.Delay(100000);
}

await still blocks current UI thread

2 Answers2

Edit :

Linked