protected override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            
            //1.先检查用户的cookie是否包含登录信息,cookie的值即是qq用户的openid
            //2.根据用户cookie去服务器检索
            //3.如果用户cookie跟服务器上一致，则表明己登录。
            if (Request.Cookies["user_qq_cookie"] != null)
            {
                //有cookie，表明己登录过了
                //1）先取cookie，这里获取的cookie即为A应用写入的cookie，可以正常获取
                string user_qq_cookie = Request.Cookies["user_qq_cookie"].Value;
                //2)根据cookie到服务器缓存中取数据。
                //现在就是发现这里CacheHelper.Get获取不到数据。
                object obj = CacheHelper.Get("qq_" + user_qq_cookie);
                //3）
                if (obj != null)//说明服务器中有这个缓存
                {
                   //这里的user为一个实体对象
                    user = (Passport_OAuth_User_Model)obj;
                    ViewBag.user = user;
                }
                else
                {
                   //程序直接走到这
                    user = null;
                }

            }
            else
            {
                //没有cookie
                user = null;
            }
            base.OnActionExecuting(filterContext);
        }                                 

private static readonly MemcachedClient memcachedClient;

        static MemCachedHelper()
        {
            if(string.IsNullOrWhiteSpace(ConfigurationManager.AppSettings["memcachedServer"]))
            {
                throw new Exception("请在web.config的appsetting中配置memcached服务器信息！");
            }
            string[] servers = ConfigurationManager.AppSettings["memcachedServer"].Split(new char[','], StringSplitOptions.RemoveEmptyEntries);

            //初始化池
            SockIOPool pool = SockIOPool.GetInstance();
            pool.SetServers(servers);
            pool.InitConnections = 3;
            pool.MinConnections = 3;
            pool.MaxConnections = 5;
            pool.SocketConnectTimeout = 1000;
            pool.SocketTimeout = 3000;
            pool.MaintenanceSleep = 30;
            pool.Failover = true;
            pool.Nagle = false;
            pool.Initialize();
            memcachedClient = new Memcached.ClientLibrary.MemcachedClient();
            memcachedClient.EnableCompression = false;
        }


        public object Get(string key)
        {
          return  memcachedClient.Get(key);
        }

        public void Set(string key, object objObject)
        {
            memcachedClient.Set(key, objObject);
        }