How do I cancel a Blocked Task in C# using a Cancellation Token?

Question

I have a Task which is always blocked and I have a CancellationToken passed into it which is used to cancel the task. However the Continuation task is never executed which is set to execute on Task's cancellation. The code is:

    _tokenSrc = new CancellationTokenSource();
    var cnlToken = _tokenSrc.Token;

    Task.Run(() => 
          // _stream.StartStream() blocks forever  
          _stream.StartStream(), cnlToken)
        .ContinueWith(ant =>
        {
            _logger.Warn("Stream task cancellation requested, stopping the stream");
            _stream.StopStream();
            _stream = null;
            _logger.Warn("Stream stopped and task cancelled");
        }, TaskContinuationOptions.OnlyOnCanceled);

Later somewhere else in the code ...

_tokenSrc.Cancel();

The reason I had to use a Task for _stream.StartStream() is that this call blocks forever (an api on which I have no control, note that _stream refers to a thirdparty Api which streams data from a webservice) so I had to invoke it on another thread.

What is the best way to cancel the task?

Answer 1

[UPDATE]

I changed the code to below which fixed the problem:

Task.Run(() =>
{
    var innerTask = Task.Run(() => _stream.StartStream(), cToken);
    innerTask.Wait(cToken);
}, cToken)
.ContinueWith(ant =>
{
    _logger.Warn("Stream task cancellation requested, stopping the stream");
    _stream.StopStream();
    _stream = null;
    _logger.Warn("Stream stopped and task cancelled");
}, TaskContinuationOptions.OnlyOnCanceled);