A task that will never end until cancellation is requested

Question

I need a task that never ends until cancellation is requested. At the moment the simplest way to do that is:

var cancellation = new CancellationTokenSource();

var task = Task.Factory.StartNew(async () =>
{
    while (true)
    {
        await Task.Delay(10000, cancellation.Token);
    }
}, cancellation.Token).Unwrap();

What I don't like is a call to Task.Delay method because it requires limited time interval for waiting.

Is there more elegant solution?

Answer 1

You should be able to subscribe to the cancellation of the token and complete the task then:

public static Task UntilCancelled(CancellationToken tok)
{
    var tcs = new TaskCompletionSource<object>();
    IDisposable subscription = null;
    subscription = tok.Register(() =>
    {
        tcs.SetResult(null);
        subscription.Dispose();
    });

    return tcs.Task;
}

Answer 2

As an alternative to TaskCompletionSource with token.Register, here are some one-liners:

var task = new Task(() => {}, token); // don't do task.Run()!

Or, simply this:

var task = Task.Delay(Timeout.Infinite, token);

There's even a nice optimization for Timeout.Infinite in the current Task.Delay implementation.