如何使用存储库模式将 EF 对象转换为 WCF 模型

Question

I'm trying to build my first (Rest?) WCF service on .NET with entity framework 6 following Repository pattern.

So it is supposed that I have to expose only simple object from the service, not the entire EF classes, right?

So I build a simple Model Like this, that represent some field from a database table:

[DataContract]
public class FormasPagoModel
{
    [DataMember]
    public int ID { get; set; }

    [DataMember]
    public string FormaPago { get; set; }        
}

This is the data type returned by my WCF service method. So I whant a method GetbyID on my service. To do so, i create an interface:

public interface IRepository<T> where T:class
{
    T GetEntityByID(int Key);
}

and a Repository abstract class:

public abstract class Repository<T> : IRepository<T> where T : class
{
    protected readonly OhmioNETEntities context = new OhmioNETEntities();

    public T GetEntityByID(int Key)
    {         
        return context.Set<T>().Find(Key);
    }
}

and a concrete implementation (ANX_FormasPago is my EF Class that is linked to a database table):

public class FormasPagoRep : Repository<ANX_FormasPago>
{
}    

Finally my WCF Service class

public class WCFService
{
    public FormasPagoModel FormasPago_GetbyID(int Key)
    {            
        ANX_FormasPago EFEntity = new FormasPagoRep().GetEntityByID(Key);

        return new FormasPagoModel
        {
            ID = EFEntity.ID_FormaPago,
            FormaPago = EFEntity.FormaPago,
        };
    }
}

As you can see, internally I get an EF class of type ANX_FormasPago and transform it to FormasPagoModel. Of course if I need for instance FormasPago_Save, i need to write the exact oposite code that is transform my Model(FormasPagoModel) to EF class(ANX_FormasPago)

With this code, I end up having, for each database table:

A) An EF class.

B) A Simplified Model class.

C) A concrete Repository.

D) A WCF Service method for each method.

So, I'm I in the right path here? Or am i just complicating things up.

Answer 1

I think, you're almost there. In my opinion you are actually missing one layer ( Business logic ). It's not the responsibility of your WCF service to get data from repository and convert it to a different type. The reason is that in many cases the creation of the final model object can be much more complex. I wouldn't like to clutter the WCF service with that.

Ideally the architecture would look like that:

WCF --> Business Logic --> Repository --> Entity Framework

Every layer can only talk to the layer directly on it's right .

• Repository returns filtered EF entities
• Business processes them (can use multiple repositories, perform calculations and other stuff)
• Business returns simple DTO objects ( Business should not reference WCF)
• WCF grabs DTOs and maps them to WCF models (I'd use AutoMApper for that btw). This mapping is necessary as Business doesn't reference WCF components (DataContract and DataMember attributes are not accessible in Business ).
• WFC releases models to the web

Also I wouldn't bother to have an abstract / base / generic repository. Sooner or later you'll end up having some ugly workarounds to handle not compatible entities ( Refused bequest problem).

Ultimately you'll end up having even more classes than you proposes, but each of them will have single responsibility . They'll be simpler, easier to test and more reusable (eg you can replace WCF layer and use WPF or MVC instead without touching different layers).