大部分完成，还有写要解决的问题

AIStudio.Wpf.DiagramDesigner.Demo/ViewModels/SimpleViewModel.cs

@@ -32,6 +32,8 @@ namespace AIStudio.Wpf.DiagramDesigner.Demo.ViewModels
 
             ConnectionViewModel connector2 = new ConnectionViewModel(node2.RightConnector, node3.RightConnector, DrawMode.ConnectingLineStraight, RouterMode.RouterOrthogonal);
             DiagramViewModel.DirectAddItemCommand.Execute(connector2);
+
+            DiagramViewModel.ClearSelectedItemsCommand.Execute(null);
         }
     }
 }