PartManager.Nodes does not contain the newly added node

When does PartManager.Nodes get updated while adding the new node by calling GraphLinksModel.AddNode() ?

I have added a new node by calling GraphLinksModel.AddNode() and called GraphLinksModel CommitTransaction().

Not able to find the corresponding Node for the via PartManager.Nodes.

BTW, I am trying to access Node to set the rotation angle for the node. Is there anyother alternative for setting rotation angle ?

Why not use a Binding?

          go:Node.RotationAngle="{Binding Path=Data.Angle, Mode=TwoWay}"
          go:Part.Rotatable="True"