static class EventManager
    {
        protected class CallbackInfo // Impossible!
        {
            private Callback callback;
            public CallbackInfo(Callback cb)
            {
                callback = cb;
            }
        }
        public delegate void Callback(Guid id);
        private static Dictionary<Guid, CallbackInfo> callbacks = new Dictionary<Guid, CallbackInfo>(); // Need non-static classes here