如何使用取消令牌取消C＃中的阻止任务？ [英] How do I cancel a Blocked Task in C# using a Cancellation Token?

问题描述

我有一个总是被阻止的任务，并且有一个CancellationToken传递给它，用于取消任务。但是，Continuation任务永远不会执行，而是设置为在Task取消后执行。代码是：

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);

稍后在代码中的其他地方...

Later somewhere else in the code ...

_tokenSrc.Cancel();

我不得不对_stream.StartStream（）使用Task的原因是，此调用将永远阻塞（一个我无法控制的api，请注意_stream指的是从网络服务流式传输数据的第三方Api），所以我不得不在另一个线程上调用它。

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.

什么取消任务的最佳方法是什么？

What is the best way to cancel the task?

推荐答案

[更新]

我将代码更改为以下代码以解决问题：

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);

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