微信公众平台开发：解决用户上下文（Session）问题

/// <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);
    }
}