Question

I’ve built a REST API with the WCF Web API Preview and I wanna build a library with the classes that you pass to this API (Just to make the .Net developers life easier). The should be simple POCO classes without much functionality.

But on the receiver side it would make sense for me to add some functionality to these classes. I have an example below:

[WebInvoke(UriTemplate = "", Method = "POST")]
public Supertext.API.Order Create(Supertext.API.Order apiOrder)
{

And this is an example POCO class:

public class Order
{
    public string Service { get; set; }

    public string OrderTitle { get; set; }

    public string Currency { get; set; }
}

Now, what’s a good way to extend this class on the server side?
I guess using a subclass would not work.
Delegates?
Actually have two different versions of the class? One for clients and one for the server?

What do other people do?

Answer 1

The problem with adding extra functionality to this POCO class is you are turning it into a domain object. The nature of this domain object will now be constrained by the fact that, essentially, this class acts as the definition of the interface into the operation. Changing details about this class will potentially break clients.

It is a far cleaner model to keep this class purely as a Data Transfer Object whose single responsibility is aiding the bridging of the wire format to objects and use a mapper such as AutoMapper to map the data from the DTO to a real domain object. The real domain object is fully under your control and you can happily refactor it without threatening a cascading effect to your service consumers