private void cmbAdd_SelectedIndexChanged(object sender, EventArgs e)
 {
     if (cmbAdd.SelectedIndex == 1)
     {
         AddNode ae = new AddNode("Add Node");
         ae.d += new AddNode.MyDel(ResetPictureBoxImage);
         ae.d += new AddNode.MyDel(CreateDynamicPoint);
         ae.ShowDialog();
         SetComboBox();
     }
     if (cmbAdd.SelectedIndex == 2)
     {
         AddEdge_DeleteEdge ad = new AddEdge_DeleteEdge("Add Edge");
         ad.ShowDialog();
     }
 }
        private void btnDelete_Click(object sender, EventArgs e)
        {
            AddEdge_DeleteEdge ad = new AddEdge_DeleteEdge("Delete Edge");

            ad.ShowDialog();
        }