public static int add(HoaDonNXB hoadon) { try { using (EntitiesDataContext db = new EntitiesDataContext()) { var hd = new HOADONNXB { masonxb = hoadon.MaSoNXB, ngaylap = hoadon.NgayLap, tongtien = hoadon.ChiTiet.Sum(ct => ct.SoLuong * ct.DonGia), trangthai = 0 }; db.HOADONNXBs.InsertOnSubmit(hd); db.SubmitChanges(); foreach (ChiTietHoaDonNXB ct in hoadon.ChiTiet) { ChiTiet.add(ct, hd.masohoadon); } return(hd.masohoadon); } } catch (Exception ex) { Console.WriteLine(ex.Message); return(0); } }