C# 取消一个异步

CancellationTokenSource 和 CancellationToken。 包含命名空间：using System.Threading.Tasks;。

class CancellationPractice
{
    static void Main()
    {
        CancellationTokenSource cts = new CancellationTokenSource();
        CancellationToken token = cts.Token;

        Myclass mc = new Myclass();
        Task t = mc.RunAsync(token);

        //Thread.Sleep(1000);
        //cts.Cancel();

        t.Wait();
        Console.WriteLine($"Was Canceled:{token.IsCancellationRequested}");
        Console.ReadKey();
    }
}

class Myclass
{
    public async Task RunAsync(CancellationToken ct)
    {
        if (ct.IsCancellationRequested) return;
        await Task.Run(() => CycleMethod(ct), ct);
    }

    void CycleMethod(CancellationToken ct)
    {
        Console.WriteLine("开始执行 CyleMethod");
        const int max = 5;
        for (int i = 0; i < max; i++)
        {
            if (ct.IsCancellationRequested) return;
            Thread.Sleep(2000);
            Console.WriteLine($"    {i + 1} of {max} 循环完成。");
        }
    }
}

取消主函数的两行注释后的输出：

开始执行 CyleMethod
    1 of 5 循环完成。
Was Canceled:True

可见只完成了一项任务。

参考:

《C# 图解教程》异步