Question

I’ve got the WCF web method M that returns the class A. The web method is configured to use the JSON serializer.

Now to the question: I’ve got the class B that is the immediate specialization of A. I want to return B, but the request fails if I do.

What do I need to do to make this work, if it’s even possible?

This is essentially my problem in scribbled code:

[WebMethod]
A M();

public A M() {
   return new B(); // <-- no response on the client
} 

[DataContract]
class A { 
    [DataMember]
    bool Foo;
}

[DataContract]
class B : A {

}

Answer 1

The first thing to try would be:

[DataContract, KnownType(typeof(B))]
class A { 
    [DataMember]
    bool Foo;
}