#region 自定义ViewState
        /// <summary>
        /// 指示服务器控件是否正在跟踪其视图状态更改
        /// </summary>
        private bool _isTrackingViewState;
        /// <summary>
        /// 创建StateBag类型对象
        /// </summary>
        private StateBag _viewState;
        /// <summary>
        /// 建立ViewState对象
        /// </summary>
        protected virtual StateBag ViewState
        {
            get
            {
                if (_viewState == null)
                {
                    //如果未对其赋值，则返回空对象
                    _viewState = new StateBag(false);
                    if (_isTrackingViewState)
                    {
                        ((IStateManager)_viewState).TrackViewState();
                    }
                }
                return _viewState;
            }
        }
        #endregion

        #region 自定义类型状态管理
        bool IStateManager.IsTrackingViewState
        {
            get
            {
                return _isTrackingViewState;
            }
        }

        void IStateManager.LoadViewState(object savedState)
        {
            if (savedState != null)
                ((IStateManager)ViewState).LoadViewState(savedState);
        }

        object IStateManager.SaveViewState()
        {
            object savedState = null;
            if (_viewState != null)
            {
                savedState = ((IStateManager)_viewState).SaveViewState();
            }
            return savedState;
        }

        void IStateManager.TrackViewState()
        {
            _isTrackingViewState = true;
            if (_viewState != null)
            {
                ((IStateManager)_viewState).TrackViewState();
            }
        }
        #endregion