Find current selection's subobjects' ids in RhinoCommon

@dale
When working in a model I want to read the currently selected objects.
No problem at all when no subobjects are selected.

In case subobjects are selected (and in my particual case it would be parts of nested blocks), I would like I am trying to find out which block the selected objects belongs to.

I just saw that @lars has answered this question some time ago here.

I tried this a few days ago though and it did not work.
(Might try this again right now).