private void button1_Click(object sender, EventArgs e) { // Show 3D cuboid forms Console.WriteLine("Showing 3D Cuboid forms..."); Form_3Dcuboid form_3DcuboidA = new Form_3Dcuboid(); form_3DcuboidA.Text += " A"; BackgroundWorker backgroundWorkerA = new BackgroundWorker(); backgroundWorkerA.DoWork += new DoWorkEventHandler(delegate { form_3DcuboidA.ShowDialog(); }); backgroundWorkerA.RunWorkerAsync(); }