using System;

using System.Threading;

using System.Threading.Tasks;

​

namespace ConsoleApplication

{

    public class Program

    {

        static async Task TestAsync()

        {

            Console.WriteLine("Enter TestAsync");

            var awaiter = new Awaiter();

            //var hold = GCHandle.Alloc(awaiter);

​

            var i = 0;

            while (true)

            {

                await awaiter;

                Console.WriteLine("tick: " + i++);

            }

            Console.WriteLine("Exit TestAsync");

        }

​

        public static void Main(string[] args)

        {

            Console.WriteLine("Press Enter to exit...");

            var task = TestAsync();

            Thread.Sleep(1000);

            GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);

            Thread.Sleep(1000);

            GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);

            Console.ReadLine();

        }

​

        // custom awaiter

        public class Awaiter : 

            System.Runtime.CompilerServices.INotifyCompletion

        {

            Action _continuation;

​

            public Awaiter()

            {

                Console.WriteLine("Awaiter()");

            }

​

            ~Awaiter()

            {

                Console.WriteLine("~Awaiter()");

            }

​

            // resume after await, called upon external event

            public void Continue()

            {

                var continuation = Interlocked.Exchange(ref _continuation, null);

                if (continuation != null)

                    continuation();

            }

​

            // custom Awaiter methods

            public Awaiter GetAwaiter()

            {

                return this;

            }

​

            public bool IsCompleted

            {

                get { return false; }

            }

​

            public void GetResult()

            {

            }

​

            // INotifyCompletion

            public void OnCompleted(Action continuation)

            {

                Volatile.Write(ref _continuation, continuation);

            }

        }

    }

}