private void nhàCungCấpToolStripMenuItem_Click(object sender, EventArgs e)
{
NhaCungCap frm = new NhaCungCap();
frm.MdiParent = this;
frm.Show();
}
private void buttonItem5_Click(object sender, EventArgs e)
{
NhaCungCap ncc = new NhaCungCap();
ncc.MdiParent = this;
ncc.Show();
// this.Hide();
}