OK, i got it ...
I should read the manual more careful ;)
the Keyword is objectCollector
An implementation of the IObjectCollector interface used to
calculate the object network for each of the root objects. It can also
specify that objects referenced by the "root objects" need to be copied
and added to the container. In this case the "root objects" are added
to both, the named list and the container, whereas the referenced
objects are added only to the container.
This parameter can be null, in which case only the root objects are added to the container.