public ActionResult Add(SANPHAM_CUAHANG model)
        {
            var SanPhamCuaHang = db.SANPHAM_CUAHANG.Find(model.MaSPCH);

            db.SANPHAM_CUAHANG.Add(model);
            db.SaveChanges();
            return(RedirectToAction("Index"));
        }
        public ActionResult Edit(SANPHAM_CUAHANG model)
        {
            var obj = db.SANPHAM_CUAHANG.Find(model.MaSPCH);

            obj.MaSPCH    = model.MaSPCH;
            obj.SoLuong   = model.SoLuong;
            obj.MaSanPham = model.MaSanPham;
            obj.MaCuaHang = model.MaCuaHang;
            db.SaveChanges();
            return(RedirectToAction("index", model));
        }