/// <summary>
    /// 微信消息上下文（单个用户）接口
    /// </summary>
    /// <typeparam name="TRequest">请求消息类型</typeparam>
    /// <typeparam name="TResponse">响应消息类型</typeparam>
    public interface IMessageContext<TRequest,TResponse>
        where TRequest : IRequestMessageBase
        where TResponse : IResponseMessageBase
    {
        /// <summary>
        /// 用户名（OpenID）
        /// </summary>
        string UserName { get; set; }
        /// <summary>
        /// 最后一次活动时间（用户主动发送Resquest请求的时间）
        /// </summary>
        DateTime LastActiveTime { get; set; }
        /// <summary>
        /// 接收消息记录
        /// </summary>
        MessageContainer<TRequest> RequestMessages { get; set; }
        /// <summary>
        /// 响应消息记录
        /// </summary>
        MessageContainer<TResponse> ResponseMessages { get; set; }
        /// <summary>
        /// 最大储存容量（分别针对RequestMessages和ResponseMessages）
        /// </summary>
        int MaxRecordCount { get; set; }
        /// <summary>
        /// 临时储存数据，如用户状态等，出于保持.net 3.5版本，这里暂不使用dynamic
        /// </summary>
        object StorageData { get; set; }

        /// <summary>
        /// 用于覆盖WeixinContext所设置的默认过期时间
        /// </summary>
        Double? ExpireMinutes { get; set; }

        /// <summary>
        /// AppStore状态，系统属性，请勿操作
        /// </summary>
        AppStoreState AppStoreState { get; set; }

        event EventHandler<WeixinContextRemovedEventArgs<TRequest, TResponse>> MessageContextRemoved;

        void OnRemoved();
    }

    /// <summary>
    /// 微信消息上下文（单个用户）
    /// </summary>
    public class MessageContext<TRequest,TResponse>: IMessageContext<TRequest, TResponse>
        where TRequest : IRequestMessageBase
        where TResponse : IResponseMessageBase
    {
        private int _maxRecordCount;

        public string UserName { get; set; }
        public DateTime LastActiveTime { get; set; }
        public MessageContainer<TRequest> RequestMessages { get; set; }
        public MessageContainer<TResponse> ResponseMessages { get; set; }
        public int MaxRecordCount
        {
            get
            {
                return _maxRecordCount;
            }
            set
            {
                RequestMessages.MaxRecordCount = value;
                ResponseMessages.MaxRecordCount = value;

                _maxRecordCount = value;
            }
        }
        public object StorageData { get; set; }

        public Double? ExpireMinutes { get; set; }

        /// <summary>
        /// AppStore状态，系统属性，请勿操作
        /// </summary>
        public AppStoreState AppStoreState { get; set; }

        public virtual event EventHandler<WeixinContextRemovedEventArgs<TRequest, TResponse>> MessageContextRemoved = null;

        /// <summary>
        /// 执行上下文被移除的事件
        /// 注意：此事件不是实时触发的，而是等过期后任意一个人发过来的下一条消息执行之前触发。
        /// </summary>
        /// <param name="e"></param>
        private void OnMessageContextRemoved(WeixinContextRemovedEventArgs<TRequest, TResponse> e)
        {
            EventHandler<WeixinContextRemovedEventArgs<TRequest, TResponse>> temp = MessageContextRemoved;

            if (temp != null)
            {
                temp(this, e);
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="maxRecordCount">maxRecordCount如果小于等于0，则不限制</param>
        public MessageContext(/*MessageContainer<IRequestMessageBase> requestMessageContainer,
            MessageContainer<IResponseMessageBase> responseMessageContainer*/)
        {
            /*
             * 注意：即使使用其他类实现IMessageContext，
             * 也务必在这里进行下面的初始化，尤其是设置当前时间，
             * 这个时间关系到及时从缓存中移除过期的消息，节约内存使用
             */

            RequestMessages = new MessageContainer<TRequest>(MaxRecordCount);
            ResponseMessages = new MessageContainer<TResponse>(MaxRecordCount);
            LastActiveTime = DateTime.Now;
        }

        public virtual void OnRemoved()
        {
            var onRemovedArg = new WeixinContextRemovedEventArgs<TRequest, TResponse>(this);
            OnMessageContextRemoved(onRemovedArg);
        }
    }

    public class CustomMessageContext : MessageContext<IRequestMessageBase,IResponseMessageBase>
    {
        public CustomMessageContext()
        {
            base.MessageContextRemoved += CustomMessageContext_MessageContextRemoved;
        }

        /// <summary>
        /// 当上下文过期，被移除时触发的时间
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void CustomMessageContext_MessageContextRemoved(object sender, Senparc.Weixin.Context.WeixinContextRemovedEventArgs<IRequestMessageBase,IResponseMessageBase> e)
        {
            /* 注意，这个事件不是实时触发的（当然你也可以专门写一个线程监控）
             * 为了提高效率，根据WeixinContext中的算法，这里的过期消息会在过期后下一条请求执行之前被清除
             */

            var messageContext = e.MessageContext as CustomMessageContext;
            if (messageContext == null)
            {
                return;//如果是正常的调用，messageContext不会为null
            }

            //TODO:这里根据需要执行消息过期时候的逻辑，下面的代码仅供参考

            //Log.InfoFormat("{0}的消息上下文已过期",e.OpenId);
        }
    }