nested Parallel.For Loop - Cancellation.Token doesn't work

I have the following problem: I have a tight loop (on purpose) which starts on a click event in the MainWindow.cs of my WPF application.

Now, a stop event triggered by another button should stop the tight loop and end the Task.

In my tight loop I have a Parallel.For loop.The idea is that I have to do a certain amount of things simultaneously (Parallel.For) and this over and over again (tight loop). I don't know if this is the best approach but it's the only one that I had, however it works :) .

I have a problem with the Cancellation.Token which doesn’t seem to do anything. How do I stop the loop and end the Task correctly.

Here’s my code:

var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
CancellationToken token = cts.Token;

ParallelOptions po = new ParallelOptions();
po.CancellationToken = cts.Token;
po.MaxDegreeOfParall开发者_高级运维elism = System.Environment.ProcessorCount;

Task dlTask = Task.Factory.StartNew( 
() =>
{
  do
  {
    Parallel.For(0, num, po, i => {
      if (!token.IsCancellationRequested)
      {
        // do work
      }
    });
  }
  while (!token.IsCancellationRequested);

}, token, TaskCreationOptions.LongRunning, TaskScheduler.Default);

dlTask.ContinueWith(prev => 
{
     //clean up
}, uiScheduler);

I tried it with po.CancellationToken.IsCancellationRequested and without and it didn't stop.

private void btnStop_Click(object sender, RoutedEventArgs e)
{
  if (cts.IsCancellationRequested || po.CancellationToken.IsCancellationRequested)
  {
    cts.Cancel();
  }
}

UPDATE: Solution thanks to Damien_The_Unbeliever:

private void btnStop_Click(object sender, RoutedEventArgs e)
{
  cts.Cancel();
}

You need to call cts.Cancel() in the event handler for your stop button. This will tell your cancelation token that you have requested cancellation.