取消所有异步任务 [英] Cancel all async tasks

问题描述

是否有可能取消所有异步方法，不知道什么是当前正在运行的

Is it possible to cancel all async methods, without knowing what is currently running?

例如我有几个类，可能运行的异步任务：？

For example I have several classes that may run async tasks:

class Class1
{
    public async void SomeTask()
    {
        for (int i = 0; i < 5; i++)
        {
            // Doing some job
            await Task.Delay(2000);
        }
    }
}

class Class2
{
    public async void ContinuouslyTask()
    {
        for (;;)
        {
            // Doing some job on background
            await Task.Delay(1000);
        }
    }
}

和我要关掉所有的异步任务，在此之前我会注销：

And I want turn off every async task, before I will logout:

class Program
{
    static void Main(string[] args)
    {
        var p = new Program();
        var c1 = new Class1();
        var c2 = new Class2();

        c1.SomeTask();
        c2.ContinuouslyTask(); 

        while (Console.ReadKey().Key != ConsoleKey.Enter) { }

        p.Logout();
    }

    private void Logout()
    {
        // Cancel all async tasks

        // And do logout work
    }
}

是否有可能做到这一点，但不保存任务分为查询？

Is it possible to do this, without saving tasks into query?

推荐答案

这基本上是扩大@FrankFajardo答案提供一个具体的例子。
当您在传递的CancellationToken ，你还需要监视它从外部的任何取消请求。它看起来是这样的：

This is basically extending @FrankFajardo answer to provide a concrete example. When you pass in a CancellationToken, you also need to monitor it for any cancellation request from the outside. It will look like this:

class Class1
{
    public async Task SomeTaskAsync(CancellationToken cancellationToken)
    {
        for (int i = 0; i < 5; i++)
        {
            if (cancellationToken.IsCancellationRequested)
                break;
            // Doing some job
            await Task.Delay(2000);
        }
    }
}

class Class2
{
    public async Task ContinuouslyTaskAsync(CancellationToken cancellationToken)
    {
        while (!cancellationToken.IsCancellationRequested)
        {
            // Doing some job on background
            await Task.Delay(1000);
        }
    }
}

而现在，当你想取消它，您只需 CancellationTokenSource.Cancel（）调用添加到您的代码：

And now when you want to cancel it, you simply add CancellationTokenSource.Cancel() call to your code:

static void Main(string[] args)
{
    var p = new Program();
    var c1 = new Class1();
    var c2 = new Class2();

    var cancellationTokenSource = new CancellationTokenSource();
    var someTask = c1.SomeTask(cancellationTokenSource.Token);
    var continuousTask = c2.ContinuouslyTask(cancellationTokenSource.Token); 

    while (Console.ReadKey().Key != ConsoleKey.Enter) { }

    cancellationTokenSource.Cancel();
    Task.WaitAll(someTask, continuousTask);

    p.Logout();
}

请注意我用 Task.WaitAll 不仅是因为这是一个控制台应用程序，其中主不可能是异步。否则，使用 Task.WhenAll 返回一个awaitable 工作。

Note I'm using Task.WaitAll only because this is a console application where Main can't be async. Otherwise, use Task.WhenAll which returns an awaitable Task.

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