Question

I want to inherit from a class which is located in a WCF Service. The Inheritance works fine (I see the properties of the base class in my child class), my problem occurs when I try to call a method from the service and pass the childtype as a parameter and not the basetype.

Base class in WCF Service (Pet):

[ServiceContract]
public interface IService
{
    [OperationContract]
    void BringPet(Pet pet);

    [OperationContract]
    void TakePet(Pet pet);

    [OperationContract]
    List<Pet> GetAllPets();
}

[DataContract]
public class Pet
{
    private string _name;
    private string _color;

    [DataMember]
    public string Name
    {
        get { return _name; }
        set { _name = value; }
    }

    [DataMember]
    public string Color
    {
        get { return _color; }
        set { _color = value; }
    }
}

Class on the client (Dog inherits from Pet):

[DataContract()]
class Dog : PetService.Pet
{
    [DataMember()]
    public bool HasPedigree { get; set; }
    [DataMember()]
    public string Race { get; set; }
}

When I try calling something like this:

        Dog dog = new Dog()
        {
            Color = "Black",
            Name = "Pluto",
            HasPedigree = true,
            Race = "Travolta"
        };

        _client.BringPet(dog);

I get a CommunicationException which says that the type Dog is not expected by the method BringPet(Pet pet).
I would solve this problem by setting the KnownType attributes on the service side, but because my service must not know the type Dog I can’t set the KnownType or ServiceKnownType attributes.

Can someone help me out?

Answer 1

I think this is very similar to this question: Service – client interface, architecture advice

As you will see, there is no really easy way to do this without making your service operation more generic.