Custom Collections with NHibernate, Part I: Who Cares?

When people speak of the object-relational impedance mismatch, they usually talk about the differences between structure, the lack of behavior in relational databases, and the complexities that mapping abstractions present. A disadvantage which receives less attention is the impact that the impedance mismatch has on keeping code free of extraneous data-driven communications. In spite of the efforts taken to avoid it, domain layer code ultimately includes some degree of coding and/or structure which was dictated by the constraints of the data layer.