private void hàngHóaToolStripMenuItem1_Click(object sender, EventArgs e)
{
HangHoa frm = new HangHoa();
frm.MdiParent = this;
frm.Show();
}
private void buttonItem6_Click(object sender, EventArgs e)
{
HangHoa hh = new HangHoa();
hh.MdiParent = this;
hh.Show();
}