c# – 取消所有异步任务

是否可以在不知道当前正在运行的内容的情况下取消所有异步方法？

例如,我有几个可以运行异步任务的类：

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);
        }
    }
}

我要在注销之前关闭每个异步任务：

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
    }
}

是否可以这样做,而不将任务保存到查询中？

解决方法:

这基本上是扩展@FrankFajardo的答案,提供一个具体的例子.
传入CancellationToken时,您还需要监视来自外部的任何取消请求.它看起来像这样：

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);
        }
    }
}

现在,当您想要取消它时,只需将CancellationTokenSource.Cancel()调用添加到您的代码中：

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();
}

注意我只使用Task.WaitAll,因为这是一个控制台应用程序,其中Main不能是异步的.否则,使用Task.WhenAll返回一个等待的任务.

标签：c,asynchronous,async-await,cancellation-token
来源： https://codeday.me/bug/20190528/1167982.html