如何取消正在等待超时而不抛出异常的任务 [英] How to cancel a task that is waiting with a timeout without exceptions being thrown

问题描述

当使用取消令牌取消具有超时（在超时结束之前）的任务时，会抛出异常。示例：

When canceling a task that has a timeout (before the timeout has ended) using a cancel token an exception is thrown. Example:

mytask.start();
bool didTaskRunInTime = mytask.wait(5 mins, _cancelToken);

这意味着我不能像下面那样去。

Which means I cannot go on like below.

//was the task cancelled
if (_cancelToken.IsCancelRequested)
{
    // log cancel from user to file etc
}

if (didTaskRunInTime )
{
    int taskResult = myTask.Result;
    // log result to file
}
else if (!_cancelToken.IsCancelRequested)
{
    // Tell user task timed out , log a message etc
}

我必须在我的catch块中做所有这些，我的代码看起来很乱。什么是正确的方法这样做？

I will have to do all this in my catch block and my code is looking messy. What is the correct way to do this?

推荐答案

您可以致电 Task.WaitAny ，其中包含 任务的数组。然后可以对任务的状态执行操作，但方法返回。示例代码：

You could call Task.WaitAny with an array of just that task. Then you can act on the status of the task, however the method returns. Sample code:

using System;
using System.Threading;
using System.Threading.Tasks;

class Test
{
    static void Main()
    {
        Task sleeper = Task.Factory.StartNew(() => Thread.Sleep(100000));

        int index = Task.WaitAny(new[] { sleeper },
                                 TimeSpan.FromSeconds(0.5));
        Console.WriteLine(index); // Prints -1, timeout

        var cts = new CancellationTokenSource();

        // Just a simple wait of getting a cancellable task
        Task cancellable = sleeper.ContinueWith(ignored => {}, cts.Token);

        // It doesn't matter that we cancel before the wait
        cts.Cancel();

        index = Task.WaitAny(new[] { cancellable },
                             TimeSpan.FromSeconds(0.5));
        Console.WriteLine(index); // 0 - task 0  has completed (ish :)
        Console.WriteLine(cancellable.Status); // Cancelled
    }
}

请注意，你应该观察异常，以避免它最终敲定时：）

Note that if the task is faulted, you should "observe" the exception in order to avoid it going bang when it's finalized :)

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