一个任务被取消。

Question

一个任务被取消。

3

我正在运行一个任务。当关闭窗口时，我试图使用取消令牌源取消该任务。错误并非每次关闭窗口时都会发生，只有有时会出现。请查看我得到的错误。

    private CancellationTokenSource dotIndicatorTokenSource;
    private void BlinkDotIndicator()
    {

        var halfPeriod = 200;

        dotIndicatorTokenSource = new CancellationTokenSource();
        Task.Factory.StartNew(() =>
        {
            while (true)
            {
                Dispatcher.Invoke(() =>
                {
                    connectionIndicatorDotImg.Visibility = Visibility.Hidden;
                });
                Thread.Sleep(halfPeriod);

                Dispatcher.Invoke(() =>
                {
                    connectionIndicatorDotImg.Visibility = Visibility.Visible;
                });

                Thread.Sleep(halfPeriod);

                if (dotIndicatorTokenSource.IsCancellationRequested)
                {
                    break;
                }

            }
        }, dotIndicatorTokenSource.Token);

    }


    private void Window_Closing(object sender, CancelEventArgs e)
    {
        if (dotIndicatorTokenSource != null)
            dotIndicatorTokenSource.Cancel();
    }

- M. Levin

1个回答

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- Austin Winstanley · Accepted Answer

运行代码时，请在操作之前、之后和之间检查是否有取消请求。这样，如果在操作期间被取消，就不会执行下一个调度程序函数。

        while (true)
        {
            if (dotIndicatorTokenSource.IsCancellationRequested)
            {
                break;
            }

            Dispatcher.Invoke(() =>
            {
                connectionIndicatorDotImg.Visibility = Visibility.Hidden;
            });
            Thread.Sleep(halfPeriod);

            if (dotIndicatorTokenSource.IsCancellationRequested)
            {
                break;
            }

            Dispatcher.Invoke(() =>
            {
                connectionIndicatorDotImg.Visibility = Visibility.Visible;
            });

            Thread.Sleep(halfPeriod);

            if (dotIndicatorTokenSource.IsCancellationRequested)
            {
                break;
            }

        }