I was using a simple WCF service with silverlight but I wanted to validate data with annotations and I didn't want to write a whole new layer in silverlight project. So I decided to switch to using a DomainService, created through generating code in the silverlight project.
Now comes the trouble. I have a parent class and about 10 derived classes. Through WCF, I was able to just use the base class. Now I am trying to use a DomainService with the base class decorated with the KnownType attribute. The problem is now those attributes get replicated in silverlight client and a compilation error is thrown. Anybody know how to use DomainService with inheritance? I want to deliver only the information from the base class.
I don't completely follow what your problem is, but this is a great tutorial on how to use Domain Services in Silverlight, and the example includes an abstract base class for all entities, similar to what I think you're doing.