public ResponseResult <List <IMUser> > GetOnlineUsers()
        {
            var result = ResponseResult <List <IMUser> > .Default();

            try
            {
                List <IMUser> onlineUsers = ChatHub2.GetOnlineUsersOnHub();
                result = ResponseResult <List <IMUser> > .Success(onlineUsers);
            }
            catch (System.Exception ex)
            {
                result = ResponseResult <List <IMUser> > .Error(
                    string.Format("获取在线用户列表失败:{0}", ex.Message)
                    );
            }
            return(result);
        }
        public ResponseResult RegisterUserConnection(IMUser user)
        {
            var result = ResponseResult.Default();

            try
            {
                //注册为新在线用户
                ChatHub2.RegisterNewOnlineUser(user);

                //获取该用户的消息列表
                var msgModel = new MessageModel();
                msgModel.PullMessageList(user);

                result = ResponseResult.Success();
            }
            catch (System.Exception ex)
            {
                result = ResponseResult.Error(
                    string.Format("注册新用户失败:{0}", ex.Message)
                    );
            }
            return(result);
        }