private void btnSale_Click(object sender, EventArgs e) { if (ns == null) { ns = new NewSale(label4.Text); ns.MdiParent = this; ns.FormClosed += new FormClosedEventHandler(ns_FormClosed); ns.Show(); } else { ns.Activate(); } }
void ns_FormClosed(object sender, FormClosedEventArgs e) { ns = null; }