How do I return an interface from a WCF Service?

Question

Lets say I have some interfaces:

public interface IFoo {
  IBar DoesStuff();
}
public interface IBar {
  string Thingo { get; }
}

I'm consuming this code throughout my code base. The IFoo process needs to be moved onto a different system (a difference of x64 vs x32), this is our reason for using WFC. My WCF service implements this interface. When I create the "service reference" the proxy stubs are created but the interface is altered.

public interface IFoo {
   object DoesStuff();
}

I tried defining IBar/Bar as both a DataService and DataContract with no difference. Is there a way to generate the proxy code using my interface?

I'm thinking if mock objects can produce a object of my interface for testing, then shouldn't I be able to get the service to honor it as well? Or did do something silly and wrong?

Answer 1

Yes. You need to reference the project containing the interface before you add the service reference. Then the interface will be re-used. The same will be true for any custom classes used - if the project containing their definitions is referenced by the client project before the service reference is added, then WCF can re-use those definitions.

You will also need to go to the Advanced tab in the Add Service Reference dialog and tick "Reuse types in referenced assemblies" to get this to work.

Answer 2

IBar needs to be concrete and a DataContract. WCF isn't about distributed objects, but rather a way to transfer data and have services work on that data. You can't return an object in WCF that has behavior.

Answer 3

Try to think of web services as being cross-platform. What would a Java client do with your interface if you returned it?