EF with POCO + WCF + WPF. Reuse POCO classes on client or use DTOs?

Question

We are developing a 3-tier application with a WPF client, which communicates through WCF with the BLL. We use EF to access our database. We have been using the default EntityObject code generator of EF, but had lots of problems and serialization issues when sending those object through the wire, and when processing and reattaching them in the BLL.

We are about to switch to the POCO template, and rewrite the data access and the communication parts of our app (we are hoping to have a cleaner architecture and less "magic code" that way.

My question is whether it is a good idea to reuse the POCO classes on the client side? Or should we create separate DTO classes? Even if they would be identical to the POCO entity classes? What are the pros/cons of the two approaches?

Answer 1

Definitely use DTOs + AutoMapper. Otherwise you'll have tons of problems with DataContractSerializer while using WCF due to circular dependencies (especially problematic with navigational properties). Even though you may omit DTOs initially, you'll be forced to used them later on due to problems mentioned above. So I would advice using proper DTOs for each tier.

Also your tier specific models will carry different attributes. You may also need to modify (i.e. specialize) the data that you carry up in each tier. So if your project is large enough (or have the prospect to be so), use DTOs with proper naming and place them in proper locations (i.e. not all in the same assembly).