private void btnShowSPQL_Click(object sender, EventArgs e)
        {
            FormSanPham f = new FormSanPham();

            Hide();
            f.ShowDialog();
            Show();
        }
        private void btnShowSanPhamQL_Click(object sender, EventArgs e)
        {
            FormSanPham f = new FormSanPham();

            f.Show();
        }