private void bt_Sua_Click(object sender, EventArgs e)
{
SP.update(txt_MaSP.Text, txt_TenSP.Text, cmb_LoaiSP.SelectedValue.ToString(), cmb_MaNCC.SelectedValue.ToString(), Rtxt_ThongTin.Text, txt_GiaBan.Text, txt_BaoHanh.Text);
FSP.load();
this.Close();
}