public GraphLayoutForm OpenGraphLayout(MyNodeGroup target) { GraphLayoutForm graphForm; if (GraphViews.ContainsKey(target)) { graphForm = GraphViews[target]; } else { graphForm = new GraphLayoutForm(this, target); graphForm.FormClosed += GraphLayoutForm_FormClosed; GraphViews.Add(target, graphForm); } graphForm.Show(dockPanel, DockState.Document); return(graphForm); }