private void simplifyMeshToolStripMenuItem_Click(object sender, EventArgs e) { if (treeView1.SelectedNode.Tag is Geometry) { Geometry geom = (Geometry)treeView1.SelectedNode.Tag; frmSimplify f_simp = new frmSimplify(geom.Mesh); if (f_simp.ShowDialog() == DialogResult.OK) { geom.Mesh = f_simp.NewMesh; } } }