private void btHeDaoTao_Click(object sender, EventArgs e)
        {
            DanhSachHeDaoTao DSHDT = new DanhSachHeDaoTao();

            DSHDT.TopLevel = false;
            HienThi.Controls.Clear();
            HienThi.Controls.Add(DSHDT);
            DSHDT.Show();
        }
 private void btHeDaoTao_Click(object sender, EventArgs e)
 {
     DanhSachHeDaoTao DSHDT = new DanhSachHeDaoTao();
     DSHDT.TopLevel = false;
     HienThi.Controls.Clear();
     HienThi.Controls.Add(DSHDT);
     DSHDT.Show();
 }