private void buttonX7_Click_1(object sender, EventArgs e)
        {
            frmQuyenSach dt = new frmQuyenSach();

            dt.Show();
            this.Hide();
        }
 private void buttonX7_Click_1(object sender, EventArgs e)
 {
     frmQuyenSach dt = new frmQuyenSach();
     dt.Show();
     this.Hide();
 }