Question

I would like to declare an interface in my Web Service layer and then have the caller create objects of this interface type via proxy and use them to call the service methods.
However, when I decorate the interface with DataContract attribute, I get an error saying this attribute can only be applied to class, struct and enum. I don’t think that ServiceContract attribute makes sense, as the interface I am trying to expose is used only for data transfer purposes. I also noticed that when the interface was decorated with ServiceContract, it wasn’t displayed in the proxy class created.
What is the best practice to go about this?

Answer 1

You cannot do that. “DataContract” interface cannot be exposed as part of metadata. Also even if you share the interface (in assembly) your clients will not be able to send their implementation back to your service because receiving side needs real type for deserialized instance.