Resolution of Multiple Aggregation Components Supporting the
Same Interface
It is uncommon that two extensions expose the same interface to
ADSI. If this happens, the following rules apply:
If an interface, such as IMyInterface, is supported by
both the aggregator (ADSI) and any extension objects,
QueryInterface always returns the IMyInterface for
ADSI.
If an interface, such as IMyInterface, is not supported
by the aggregator (ADSI), but is supported by more than one
extension object, QueryInterface returns the
IMyInterface of the first extension object listed in the
registry that supports the interface.