I am struggling. Got properties that are of type ISet(of String) and I need to assign them with value.
Interfaces don't fully define objects. They only define one part of an object, and therefore you don't have enough information from the
ISet(Of String) interface on it's own to create an instance.
What you need to do is find a type that implements the interface, and create one of those...
HashSet(Of String) and
SortedSet(Of String) would both work.