We do like EntityFramework (CTP5) quite a lot and Using it along with ASP.NET MVC3.
What I dislike is;
things are mixed in together.
I can place a DisplayAttribute, RequiredAttribute, RangeAttribute, CompareAttribute together in the same class which means I am mixin in database validation, some business logic and UI alltogether. I can even place ScriptIgnore attribute to customize it as a Json DTO object. So I can use the same POCO class for Persistance, Presentation, DTO and Business Object, and as my domian model.
Which design patterns do you follow along with EF POCO + MVC3 toolset. What layers do you have?
What resposibilities do you add to your classes (Is Your POCO class also your Domain Model)
I use View Models to solve this problem. Validation and UI presentation attributes go to the view model. In this pattern the controller uses a repository to fetch an EF model, maps this EF model to a view model (I use AutoMapper for this) and passes the view model to the view. Because the view model contains all the UI presentation attributes the view behaves as expected. Each view must have its own view model. This means that you could have multiple view models associated to the same EF model but contain a different subset of properties and display formatting attributes based on the specific requirements of the view.
The process works the other way around as well: the controller receives a view model from the view as argument. It maps the view model back to a model and passes the EF model to the repository. UI validation attributes are handled on the view model because you could have different validation requirements in different views: think for example Insert/Update views. In the insert view you will be creating a new entity thus the Id property won’t be required. You won’t even have an Id property on your view model in this case. In the update view on the contrary the Id property will be required.