internal virtual void OnFinalUnsubscribe()
        {
            if (_log.IsDebugEnabled)
            {
                _log.DebugFormat("Final unsubscribe");
            }

            StopPolling(true);
            lock (SynchLock)
            {
                if (RequestHandlers.Count > 0)
                {
                    RequestHandlers.Clear();
                }
            }
        }