Cancel all asynchronous tasks

Question

Is it possible to cancel all asynchronous methods without knowing what is currently working?

For example, I have several classes that can 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);
        }
    }
}

And I want to disable every asynchronous task before I log out:

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
    }
}

Is it possible to do this without storing tasks in the request?

Answer 1

This is basically an extension of @FrankFajardo's answer to provide a concrete example. When you go through CancellationToken, you also need to track it for any cancellation request 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);
        }
    }
}

, , CancellationTokenSource.Cancel() :

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();
}

. Task.WaitAll , , Main . Task.WhenAll, Task.

Answer 2

CancellationTokenSource.

c1.SomeTask() c2.ContinuouslyTask() , , , , , .

Program.Main() CancellationTokenSource CancellationTokenSource.Token 2 , . CancellationTokenSource Program.Logout(), .

. , async void. , , xxxAsync (, DoWorkAsync).