CODEWITHSUNDEEP
c#multithreadingtask-parallel-library
Complexity
Complexity

Reputation: 5820

Why isn't a Task awaited before it get's cancelled?

I need to write a service with some complex behaviour like simultanious tasks and I'm facing an issue with.

I've written a sample in xUnit to show you the problem.

1 want to execute a task on a background, eventually start some child tasks. At a moment in time the task needs to be cancelled.

Therefore, I have the following in place:

[Fact]
public void ShouldWaitUnitTaskCompleted()
{
    Task.Factory.StartNew(() =>
    {
        while (!cancellationTokenSource.IsCancellationRequested)
        {
            Task.Delay(10000).Wait();
            TaskIsCompleted = true;
        }
    }, cancellationTokenSource.Token);

    Thread.Sleep(3000);

    cancellationTokenSource.Cancel();

    Assert.True(TaskIsCompleted);
}

}

However, the xUnit completes after 3 seconds (my thread sleep). In my task, I'm having a loop that say, as long as it's not a cancellation request delay if for 10 second.

So the behaviour I expect would be:

Why doesn't my code wait for the 10 seconds frame to pass?

Upvotes: 1

Views: 105

Answers (2)

Damien_The_Unbeliever
Damien_The_Unbeliever

Reputation: 239646

Cancel signals that cancellation has been requested.

It doesn't wait for all tasks to complete before allowing the cancelling code to carry on doing useful things - if you do want to wait for those tasks to respond, there are already mechanisms for you to do this, separately. So Cancel just does one job, and does it well.

Upvotes: 2

Cheesebaron
Cheesebaron

Reputation: 24460

You don't await your Task which you create. Hence the execution of the code just continues on to the Thread.Sleep(3000).

Upvotes: 4

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