使用Application改变用户在线状态

public List<UserStatus> SetUserStatus(string userAccount,string userName, string status, List<UserStatus> UserStatus)
        {
            #region 更改状态
            //根据用户名查找，在application中更改对应的状态。
            var query = UserStatus.Where(qu => qu.Account == userAccount);
            UserStatus temp = new DYModel.UserStatus();
            if (query.Count() > 0)
            {
                temp = query.FirstOrDefault();
                UserStatus.Remove(temp);
            }
            else
            {
                temp.Account = userAccount;
                temp.Name = userName;
            }
            temp.status=status;
            UserStatus.Add(temp);
            #endregion

            return UserStatus;
        }

protected void Session_End(object sender, EventArgs e)
        {
            //改变用户状态
            UserInfo userInfo = (UserInfo)Session["SESSION_USER_MODEL_KEY"];
            List<UserStatus> userStatus = (List<UserStatus>)Application["UserStatus"];
            Application.Lock();
            BLLUserStatus bll = new BLLUserStatus();
            //修改为离线状态（可自行修改）
            Application["UserStatus"]=bll.SetUserStatus(userInfo.Account, userInfo.Name, "0", userStatus);
            Application.UnLock();
        }