public Result<List<Diem_ett>> select_by_fields(string input, string how)
        {
            Result<List<Diem_ett>> rs = new Result<List<Diem_ett>>();
            try
            {
                List<Diem_ett> lst = new List<Diem_ett>();
                IQueryable<tbl_diem> dt = null;
                switch (how)
                {
                    case "masv":
                        dt = db.tbl_diems.Where(o => o.masv.Contains(input));
                        break;
                    case "tensv":
                        break;
                    case "mamon":
                        dt = db.tbl_diems.Where(o => o.mamon.Contains(input));
                        break;
                    case "tenmon":
                        break;
                    case "diem":
                        dt = db.tbl_diems.Where(o => o.diem.Contains(input));
                        break;
                    default:
                        break;
                }

                if (dt.Count() > 0)
                {
                    foreach (tbl_diem item in dt)
                    {
                        Diem_ett temp = new Diem_ett(item);
                        lst.Add(temp);
                    }

                    rs.data = lst;
                    rs.errorCode = ErrorCode.Sucess;
                } else
                {
                    rs.data = null;
                    rs.errorCode = ErrorCode.NaN;
                    rs.errorInfor = Constants.empty_data;
                }
                return rs;
            }
            catch (Exception e)
            {
                rs.data = null;
                rs.errorCode = ErrorCode.False;
                rs.errorInfor = e.ToString();
                return rs;
            }
        }
        public Result<List<Diem_ett>> select_all_diem()
        {
            Result<List<Diem_ett>> rs = new Result<List<Diem_ett>>();
            try
            {
                List<Diem_ett> lst = new List<Diem_ett>();
                var dt = db.tbl_diems;
                if (dt.Count() > 0)
                {
                    foreach (tbl_diem item in dt)
                    {
                        Diem_ett temp = new Diem_ett(item);
                        lst.Add(temp);
                    }

                    rs.data = lst;
                    rs.errorCode = ErrorCode.Sucess;
                }
                else
                {
                    rs.data = null;
                    rs.errorCode = ErrorCode.NaN;
                    rs.errorInfor = Constants.empty_data;
                }

                return rs;
            }
            catch (Exception e)
            {
                rs.data = null;
                rs.errorCode = ErrorCode.False;
                rs.errorInfor = e.ToString();
                return rs;
            }
        }