如何正确重置 CancellationToken? [英] How to reset a CancellationToken properly?

问题描述

今天早上我一直在玩 Async CTP 并且有一个带有 button 和 label 的简单程序.点击button，它开始更新label，停止button，它停止写入label.但是，我不确定如何重置 CancellationTokenSource 以便我可以重新启动该过程.

I have been playing round with the Async CTP this morning and have a simple program with a button and a label. Click the button and it starts updating the label, stop the button it stops writing to the label. However, I'm not sure how to reset the CancellationTokenSource so that I can restart the process.

我的代码:

public partial class MainWindow : Window
{
    CancellationTokenSource cts = new CancellationTokenSource();
    public MainWindow()
    {
        InitializeComponent();
        button.Content = "Start";
    }

    async Task DoWork(CancellationToken cancelToken)
    {
        int i = 0;
        while (!cancelToken.IsCancellationRequested)
        {
            label.Content = i++.ToString();
            await TaskEx.Delay(50, cancelToken);
        }
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        if (button.Content == "Start")
        {
            button.Content = "Stop";
            DoWork(cts.Token);
        }
        else
        {
            button.Content = "Start";
            cts.Cancel();
        }
    }
}

推荐答案

您需要重新创建 CancellationTokenSource - 一旦设置，就无法重置"它.

You need to recreate the CancellationTokenSource - there is no way to "reset" this once you set it.

这可以很简单:

private void Button_Click(object sender, RoutedEventArgs e)
{
    if (button.Content == "Start")
    {
        button.Content = "Stop";
        cts.Dispose(); // Clean up old token source....
        cts = new CancellationTokenSource(); // "Reset" the cancellation token source...
        DoWork(cts.Token);
    }
    else
    {
        button.Content = "Start";
        cts.Cancel();
    }
}

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