Models just in a WCF Service or is it necessary a replica in the Client?

Question

I am building an application. I am creating a Silverlight 4 client with the help of MVVM Light. I am acquiring data from a WCF Service. At least, this is the plan.

In the WCF Service I have defined the "entities" that I need to use in my application. When in the Silverlight Client I add a reference to my WCF Service, Visual Studio recreates on the client-side all classes that were marked with the attribute [DataContract] in the service.

What I would like to know is if this is a bad practice and if it were better to create the Models inside the Client. As far as I understand, in the first case I should only create the ViewModels and the Views in the Silverlight client, whereas in the second case I should create the Views, ViewModels and Models inside the Silverlight client, and populate the Models instances with the values coming from the WCF Service.

Thank you for your help.

Cheers, G.

UPDATE

Ok, I don't think my question was clear enough as I havent not received many feedbacks. However, I'd like to provide an update on this. The answer I was looking for is "No! Data Transfer Objects!".

I was thinking to use my entity classes (the ones mapped to the DB tables) as DataContract in a WCF Service. Adding a reference to this WCF service in a client would have created all the classes decorated with DataContract on the client too.

The big problem in my case is that the data layer is based on Hibernate, which soemtimes makes extensive use at runtime of "data proxy" classes (see Castle Proxy). Well, it turned out that there is a serialization issue with these data proxies, and as far as I understood the best approach is to adopt the Data Transfer Objects pattern in order to map the "complex" entities to a similar but "lighter" class (the DTO).

I hope this can help someone else.

Have a nice day! Gianluca.

Answer 1

Have you looked at WCF RIA with Nhibernate? To try and answer the question though: I wouldn't try and return entities from the WCF service directly, I personally would create DTO's. And then I would probably map those DTO's to some sort of a client side model. So, that's what I would try and do if I wasn't able to take advantage of RIA.