private void списокСиМToolStripMenuItem_Click(object sender, EventArgs e) { if (f13 == null) { f13 = new Form13(); f13.MdiParent = this; f13.FormClosed += new FormClosedEventHandler(f13_FormClosed); f13.Show(); } else { f13.Activate(); } }
void f13_FormClosed(object sender, FormClosedEventArgs e) { f13 = null; }