class SingleThreadSyncContext : SynchronizationContext
    {
        List<(SendOrPostCallback, object)> calls = new List<(SendOrPostCallback, object)>();
        List<(SendOrPostCallback, object)> calls2 = new List<(SendOrPostCallback, object)>();
        public override void Post(SendOrPostCallback d, object state)
        {
            lock (calls)
            {
                calls.Add((d, state));
            }
        }

        public override void Send(SendOrPostCallback d, object state)
        {
            Console.WriteLine($"send on thread {Thread.CurrentThread.ManagedThreadId}");
            base.Send(d, state);
        }

        public void Tick()
        {
            List<(SendOrPostCallback, object)> callsLocked = null;
            lock (calls)
            {
                callsLocked = calls;
                calls = calls2;
                calls2 = callsLocked;
            }
            foreach (var call in callsLocked)
            {
                call.Item1(call.Item2);
            }
            callsLocked.Clear();
        }
    }


    internal class Program
    {
        static bool finish = false;
        static async void DoAsync()
        {
            Console.WriteLine($"1 curr thread {Thread.CurrentThread.ManagedThreadId}");
            Console.WriteLine($"2 curr context {SynchronizationContext.Current}");
            Thread.Sleep(10);
            await Task.Delay(100);

            Console.WriteLine($"2 curr thread {Thread.CurrentThread.ManagedThreadId}");
            Console.WriteLine($"2 curr context {SynchronizationContext.Current}");
            Thread.Sleep(10);
            await Task.Delay(100);

            Thread.Sleep(10);
            Console.WriteLine($"3 curr thread {Thread.CurrentThread.ManagedThreadId} wait");
            finish = true;
        }

        public const long ticksPerSecond = 30 * 10000;

        public static void Main(string[] args)
        {
            var context = new SingleThreadSyncContext();
            SynchronizationContext.SetSynchronizationContext(context);
            DoAsync();

            var timer = Stopwatch.StartNew();
            var timerForDt = Stopwatch.StartNew();
            while (finish == false)
            {
                var t = timer.ElapsedTicks;
                context.Tick();
                var timeToWait = ticksPerSecond - timer.ElapsedTicks;
                if (timeToWait > 0)
                    Thread.Sleep((int)timeToWait / 10000);
            }

            Console.ReadKey();
        }
    }