We're using interfaces to represent entity classes in our domain model. We have concrete implementations of these by virtue of using LinqToSql. We have added a factory method to each LinqToSql class which our service layer uses to instantiate a new entity (note; as opposed to the controller's DataBind attribute doing it).
MonoRail's default DataBinder implementation will ignore properties that are defined as interfaces.
Ideally, we don't want to instantiate our data-layer classes in MonoRail - the whole point of the interfaces is to separate these concerns.
Also, we don't really want to create another set of non-LinqToSql concrete classes whose only job is to translate between layers.
It's the end of a really long day over here; please can someone have mercy and point us at the parts of IDataBinder that we should overload with our own implementations, or hint at other approaches we might attempt? ;-)
You should be looking at IParameterBinder. take a look at a post I've written on the subject