private void quảnLýĐoànViênToolStripMenuItem_Click(object sender, EventArgs e)
        {
            frmDoanvien dv = new frmDoanvien();

            dv.Show();
        }
        private void btndv_Click(object sender, EventArgs e)
        {
            frmDoanvien dv = new frmDoanvien();

            dv.Show();
        }