When I use CancelAfter(), the Task is still running

Question

I want to use CancellationTokenSource stop the Task. My tests as follow:

Test 1 : Using Cancel() stopped the task sucessfully.

Test 2 : Using CancelAfter() d

Answer 1

The core problem is the Task won't stop once it is started.

It must be check the IsCancellationRequested.

There is one way to solve this problem:

when task is running , use Thread.CurrentThread to get the thread, and create a new Task to listen the running task's CancellationToken. In the listening function:listening the status of cancel, call thread.Abort() if cancel event is ture. Use Abort() is a unsafe way,but it can stop the task.

The code as follow:

    static void Main(string[] args)
    {
        // If the task running used 3000ms, stop.
        int timeOut = 3000;
        CancellationTokenSource source = new CancellationTokenSource();
        source.CancelAfter(timeOut);
        CancellationToken token = source.Token;
        token.Register(() =>
        {
            Console.WriteLine("Task Is TimeOut!!!!! Stop");
        });
        //start the task:
        Task.Run(() =>
        {
            Console.WriteLine("Task start");
            Thread thread = Thread.CurrentThread;
            //create a new task listening the token;
            Task.Factory.StartNew(() =>
            {
                Console.WriteLine("Listening start");
                while (!token.IsCancellationRequested)
                {
                    Console.WriteLine("Listening...");
                    Thread.Sleep(800);
                }
                Console.WriteLine("Listening End");
                thread.Abort();
            }, token);

            Stopwatch time = Stopwatch.StartNew();
            #region A long time operation：;
            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine("run...");
                Thread.Sleep(100);
            }
            #endregion
            time.Stop();
            Console.WriteLine("Task end. cost:{0}", time.ElapsedMilliseconds);
            source.Cancel();
            Console.WriteLine("Task End");
            token.ThrowIfCancellationRequested();
        }, token);
        Console.ReadLine();
    }