private void taoMaHoaDon(string ban) { DataTable dt = new DataTable(); dt = bd.laybangHoaDon(ban); if (dt.Rows.Count <= 0) { mahd = "001"; } else { int i = dt.Rows.Count; //mahd = (Convert.ToInt16(dt.Rows[i - 1]["MaHD"])+1).ToString(); i = Convert.ToInt16(dt.Rows[i - 1]["MaHD"].ToString().Substring(3, 3)) + 1; //mahd = (Convert.ToInt16(mahd) + 1).ToString(); if (i < 10) { mahd = "00"; } else if (i < 100) { mahd = "0"; } else { mahd = ""; } mahd = mahd + i.ToString(); } mahd = ban + mahd; lbl_MaHD.Text = "Mã HD: " + mahd; }