gistfile1.cs

    public class ConcurrentGateway
    {
        private ConcurrentQueue<Action> _workQueue = new ConcurrentQueue<Action>();
        private int _writeLock = 0;

        private static AutoResetEvent _waitEvent = new AutoResetEvent(false);

        protected static AutoResetEvent GetThreadWaitEvent()
        {
            //returns same event for all threads ,but we could easily provide a
            //separate event for each thread to reduce lock contention
            return _waitEvent;
        }

        public void DoSynchronized(Action act)
        {
            bool done = false; 
            var ev = GetThreadWaitEvent();
            _workQueue.Enqueue(delegate() //enqueue the work TBD
            {
                act();
                done = true;
                ev.Set();
            });
            int lk = Interlocked.CompareExchange(ref _writeLock, 1, 0);
            if (lk == 1)
            { //I'm a writer thread, do all the work now
                Action a2;
                while(_workQueue.TryDequeue(out a2)) {
                    a2();
                }
                var ov = Interlocked.CompareExchange(ref _writeLock, 0, 1);
                System.Diagnostics.Debug.Assert(ov == 0); //release
            }
            else
            { //i'm not a writer so I have to wait
                while (!done)
                {
                    ev.WaitOne();
                }
            }
        }
    }