public void CretaCoupon(NhaXuatBan nxb, List <ChiTietPhieuNhapSach> listChiTiet) { PhieuNhapSach coupon = new PhieuNhapSach(); coupon.NgayNhap = DateTime.Now.Date; string id = "PNS" + nxb.Id + DateTime.Now.ToBinary().ToString(); coupon.IdNxb = nxb.Id; coupon.Id = id; db.PhieuNhapSach.Add(coupon); db.SaveChanges(); foreach (ChiTietPhieuNhapSach item in listChiTiet) { item.IdPhieuNhap = id; Sach book = sachBL.GetBookById((int)item.IdSach); book.SoLuong += (int)item.SoLuong; db.Sach.Update(book); db.ChiTietPhieuNhapSach.Add(item); } db.SaveChanges(); }