I show the selector when the Initialize method is called, and I check if the entity factory to use is null or not, if null, I show the selector. Of course, visual studio creates an empty object, THEN calls the initialize method and THEN deserializes back the set factory. I.o.w.: the selector should he shown at another time, but the only way to do that is by using a ToolItem object which is a facade and dragged from teh toolbox onto the form, creates the proper component and shows teh selector for the first time.
Problem is though... the type to create is not known to the toolitem, as far as I know, so if you add a derived entity collection class to the toolbox, it will not know that type. I'll try to find out if I can somehow retrieve that type and then I can fix it properly.