c# - 如何正确重置 CancellationToken？

Question

今天早上我一直在玩，Async CTP并且有一个带有 abutton和 a的简单程序label。单击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。

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();
        }
    }
}

score 99 · Accepted Answer

您需要重新创建CancellationTokenSource- 一旦设置它，就无法“重置”它。

这可能很简单：

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();
    }
}

score 9 · Accepted Answer

我遇到了同样的问题，我发现解决它的最佳方法是在调用该方法之前新创建取消令牌源。

这就是我点击开始按钮时所做的：

cancellationTokenSource = new CancellationTokenSource();
cancellationToken = cancellationTokenSource.Token;
Task.Factory.StartNew(StartUpload, cancellationToken);

我将同一个按钮的标题更改为取消，当点击取消时，我调用

cancellationTokenSource.Cancel();

这是完整的代码：

if (button3.Text != "&Start Upload")
{
    cancellationTokenSource.Cancel();
}
else
{
    try
    {
        cancellationTokenSource = new CancellationTokenSource();
        cancellationToken = cancellationTokenSource.Token;
        Task.Factory.StartNew(StartUpload, cancellationToken);
    }
    catch (AggregateException ex)
    {
        var builder = new StringBuilder();
        foreach (var v in ex.InnerExceptions)
            builder.Append("\r\n" + v.InnerException);
        MessageBox.Show("There was an exception:\r\n" + builder.ToString());
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

score 3 · Accepted Answer

现在，使用 .NET 6，您可以使用查看此问题的TryReset()方法和CancellationTokenSource.cs了解更多详细信息。Attempts to reset the CancellationTokenSource to be used for an unrelated operation.

c# - 如何正确重置 CancellationToken？

3 回答 3

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