WCF charset=utf-8 of the response message does not match the content type of the binding (application/soap+xml; charset=utf-8)

Question

I\'m hosting a WCF service in IIS 7.5 using .NET 4.0. I also have a WPF application that I am using as my client that was built with Visual Studio 2010 and .NET 4.0. I add

Answer 1

I got this problem after I added a method that returned a collection of instances of a base class that didn't have a [KnownType] attribute that would resolve to a concrete instance. With the [KnownType] attribute in place the problem disappeared.

[ServiceContract]
public interface IService {
    [OperationContract]
    IEnumerable GetItems();
}

[DataContract]
// [KnownType(typeof(RealItemA))] <--- without these attributes you will get a problem
// [KnownType(typeof(RealItemB))]
public class ItemBase {
}

[DataContract]
public class RealItemA : ItemBase {
}

[DataContract]
public class RealItemB : ITemBase {
}