//Chi Tiết Hóa Đơn
        public ActionResult ChiTietHD(int id_hd)
        {
            List <tbl_ProductOfBill> cthd   = ddd.tbl_ProductOfBills.Where(ct => ct.BillId == id_hd).ToList();
            tbl_ProductOfBill        lay_id = ddd.tbl_ProductOfBills.FirstOrDefault(ct => ct.BillId == id_hd);

            Session["cthd"]      = lay_id.BillId;
            Session["TrangThai"] = lay_id.tbl_Bill.Status;
            return(View(cthd));
        }
        public ActionResult ThemCTHD1(FormCollection collection, tbl_ProductOfBill cthd)
        {
            var t_sohd    = collection["sohoadon"];
            var t_tensp   = Request.Form["tensp"];
            var t_soluong = collection["soluong"];

            cthd.BillId    = Convert.ToInt32(t_sohd);
            cthd.ProductId = Convert.ToInt32(t_tensp);
            cthd.Number    = Convert.ToInt32(t_soluong);

            ddd.tbl_ProductOfBills.InsertOnSubmit(cthd);
            ddd.SubmitChanges();
            return(this.ThemCTHD1());
        }