R – NHibernate mapping: one-to-many where

Check out this blog post: How to map a tree in NHibernate

OK! After much playing around with mapping files I have found an undocumented issue (at least I could find no mention of the error I was committing).

When using subclassing the parent class cannot contain a mapping for a property that is the discriminator column. If you look at the second mapping document I posted it shows the super class and the sub class. The super class's discriminator is the ObjectType column. I also map this as a property to the abstract class ObjectInRole. You cannot do this. Once this line was removed everything worked correctly (not saving the bag).

The bag seems to be an issue that is not controllable through anything I have found in documentation. I cannot find another instance of where the abstract class is saved through the mapping. It appears that NHibernate does not know that the linking class is a UserInRole object and not a ObjectInRole object. Researching all the options that are provided for the bag node there was no apparent way to tell NHibernate what type of class it was linking through to make the many-to-many association. From what I can tell it doesn't care, but more or less treats the table as just a table, not a mapped object. If there was a way to tell it append something for the insert then maybe it would be possible, but I have not seen any information regarding this.