protected void ddTP_SelectedIndexChanged(object sender, EventArgs e)
        {
            XemDSKho.Visible = true;
            int masp = int.Parse(ddTP.SelectedValue);
            DAO_Entity daoKH = new DAO_Entity();
            DTOSanPhamCT dtosp = daoKH.LayGiaSPTheoMaCT(masp);
            lbgia.Text = dtosp.Gia.ToString();

            int ma = int.Parse(ddTP.SelectedValue);
            DAO_Entity dao = new DAO_Entity();
            DTOKhoSP dto = dao.LaySoLuongKhoSP(ma);
            lbSLKho.Text = dto.Soluong.ToString();
        }