How to write an “awaitable” method?

Question

I\'m finally looking into the async & await keywords, which I kind of "get", but all the examples I\'ve seen call async methods in the .Net framework, e.g. thi

Answer 1

... how I would write my own "awaitable" method.

Returning a Task is not the only way. You have an option to create a custom awaiter (by implementing GetAwaiter and INotifyCompletion), here is a great read: "Await anything". Examples of .NET APIs returning custom awaiters: Task.Yield(), Dispatcher.InvokeAsync.

I have some posts with custom awaiters here and here, e.g:

// don't use this in production
public static class SwitchContext
{
    public static Awaiter Yield() { return new Awaiter(); }

    public struct Awaiter : System.Runtime.CompilerServices.INotifyCompletion
    {
        public Awaiter GetAwaiter() { return this; }

        public bool IsCompleted { get { return false; } }

        public void OnCompleted(Action continuation)
        {
            ThreadPool.QueueUserWorkItem((state) => ((Action)state)(), continuation);
        }

        public void GetResult() { }
    }
}

// ...

await SwitchContext.Yield();