public static string MaThucDonMoi() { ThucDonDAO p = new ThucDonDAO(); string MaTDLonNhat = p.MaThucDonMoi(); //MessageBox.Show(MaSPLonNhat); if (string.IsNullOrEmpty(MaTDLonNhat)) { return("TD01"); } else { int masotiep = int.Parse(MaTDLonNhat.Substring(2));/*MaSPLonNhat.Replace('S', '')*/ //return string.Format("S{0:4}", masotiep + 1); return("TD" + (masotiep + 1).ToString("00")); } }