Lack of object properties

I'm getting an error while trying to get object properties such as UID's in the custom script

Dim Container as UNSContainer = Session.Source.Get(Of UNSContainer)(New VI.DB.DbObjectKey(ContainerKey))

ContainerKey is the XObjectKey of the ADSContainer object.

What I found is that Container variable has ADSContainer object type instead of UNSContainer

I have checked it on OIM 8.2 and 8.2.1