private void quảnLýKháchHàngToolStripMenuItem_Click(object sender, EventArgs e)
        {
            frm_QLKhachHang frmkh = new frm_QLKhachHang();

            frmkh.Activate();
            frmkh.ShowDialog();
        }
        private void toolStripButton1_Click(object sender, EventArgs e)
        {
            frm_QLKhachHang frmkh = new frm_QLKhachHang();

            frmkh.Activate();
            frmkh.ShowDialog();
        }