We have an application which has a UI with both WPF Windows and Windows Forms.

The WPF and Windows forms UI elements sit in separate assemblies, with the Windows forms assembly referencing the WPF assembly to allow instancing of WPF windows from the Windows forms UI.

A third assembly holds a class to bridge between the two UI assemblies so that Windows Forms can be instanced from the WPF UI (if that makes sense)

The issue we have is if an object reference is passes from one UI to the other, any changes made to the object are not seen in the calling UI (in both directions).

Is this because the two UIs are running on separate threads ?. If so how what is the best way to pass objects between the UIs and allow canges to the objects to be seen?