NHibernate many-to-many with non ID fields

Question

Hi,

I have a table A containing items with : - an identity key - a non-nullable custom hash (generated on my own)

I have a table B containing documents with : - an identity key.

I have a table C containing documents slots with : - an identity key - a foreign key to table B (document) - a nullable custom hash (so table A is implicitly linked to table C)

The goal is to implicitly link some tables to table C... so I want a many-to-many relationship between entity A and entity B through entity C with non ID fields : - Entity A.CustomHash => Entity C.CustomHash => Entity B

The generated SQL query is just fine but NHibernate complains about assigning a String (the custom key) to an Int32 (the entity C identity field I guess)

Any idea about solving this ?

Best regards,