private void butHuongDan_Click(object sender, EventArgs e)
{
HuongDan frm = new HuongDan();
frm.ShowDialog();
frm.Close();
frm.Dispose();
}
private void hướngDẫnToolStripMenuItem_Click(object sender, EventArgs e)
{
HuongDan frm = new HuongDan();
frm.Show();
}