Some question about unbounds nodes

There is a Diagram with HorContAlign=“Center”,VerContAlign=“Center”

And a TreeLayout.
Then i use Diagram.PartsModel.AddNode(new MyCustomControl()) add a Unbound node,But it isn't center the whole diagram when the node added.
The strange thing is when i Clicked any node,the whole diagram are center.
Suppose the diagram centered then if i delete the CustomControl.I also want the diagram recaculator location and recentered ,too.
How can i imp it??

I’m guessing that whenever you are making changes to a model or to model data, you are not doing so within a transaction.