How to get Castle MonoRail's DataBinder/SmartDispatcherController to bind against types containing properties that are interfaces?

Question

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? ;-)

Answer 1

Hi Peter.

You should be looking at IParameterBinder. take a look at a post I've written on the subject

Answer 2

Hi Peter,

As Ken pointed, your idea could be implemented with a custom IParameterBinder.

A solution would be to use IOC:

• resolve concrete instance of the form from it's interface
• then use IDataBinder to bind the instance to the request params

Another one would be using IDictionaryAdapter:

• generate a dto proxy for your interface
• then use IDataBinder to bind the dto proxy instance to the request params

NB: second option won't work if interface:

• is not public (hum)
• has methods
• or events
• or readonly properties
• or setonly properties

Last, I'm unsure of what is the problem exposing concrete class in controller's signature.

I myself use concrete form in controllers implementing interface defined in application layer services, it allows me to have concerns separated on both side:

• controller side is Http mapping and first level data validation of the form/command
• application layer services is business validation and processing of the form/command