public int WriteExitLog(int LogId, DateTime dt)
        {
            string sql = "Update LoginLogs set ExitTime=@dt where LogId=@LogId";

            SqlParameter[] param = new SqlParameter[]
            {
                new SqlParameter("@dt", dt),
                new SqlParameter("@LogId", LogId)
            };
            try
            {
                return(SQLHelp.Update(sql, param));
            }
            catch (SqlException ex)
            {
                throw new Exception("应用程序与数据库连接出错,具体内容: " + ex.Message);
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }