private void bánHàngToolStripMenuItem_Click(object sender, EventArgs e)
{
DatHang frm = new DatHang();
frm.MdiParent = this;
frm.Show();
}
private void buttonItem9_Click(object sender, EventArgs e)
{
DatHang dh = new DatHang();
dh.MdiParent = this;
dh.Show();
// this.Hide();
}