I have a legacy data base and a relation one-to-one between two tables. The thing is that relation uses two columns, not one. Is there some way to say in nhibernate that when ge
I'm assuming from your use of PropertyRef in the sample code that the two columns do not form a composite primary key. If that's the case, then you're out of luck because property-ref can only accept one property. Judging by the comments in issue NH-1722, this functionality apparently available in Hibernate but has not been ported to NHibernate.
Update: The schema you added looks like a many-to-many with additional data relationship between Task and Assignment. TaskProgress is the link table between Task and Assignment. If TaskProgress did not have the additional UserId field then you could model this as a simple many-to-many. Because the linking table has additional data it gets a bit more complicated.
Many-to-many with additional data is usually modeling by creating an object representing the linking table (TaskProgress) and modeling the relationship as two one-to-many relationships. That is, Task and Assignment have one-to-many relationships with TaskProgress. TaskProgress has properties for Task, Assignment, and User.