private string SinhMaTuDong() { try { string code = ""; QueriesTableAdapter queries = new QueriesTableAdapter(); string numbermax = queries.GetMaTranDauMax().ToString(); if (numbermax != "") { int temp = int.Parse(numbermax) + 1; code = "0000" + temp; code = "TD" + code.Substring(code.Length - 4); } else { code = "TD0001"; } return(code); } catch (Exception) { } return(null); }