如何在没有抛出异常的情况下取消等待超时的任务

Question

使用取消令牌取消具有超时(在超时结束之前)的任务时,将引发异常.例:

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

这意味着我不能继续下面.

//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
}

我将不得不在我的catch块中完成所有这些操作并且我的代码看起来很混乱.这样做的正确方法是什么？

Answer 1

你可以调用Task.WaitAny一个只有那个任务的数组.然后,您可以对任务的状态进行操作,但方法会返回.示例代码:

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,如果任务出现故障,您应该"观察"异常,以避免在最终确定时发生爆炸:)