DataContractSerializer KnownType attribute not being respected?

Question

I have a class that is decorated with a KnownType attribute with a type of the class. Is this not allowed?

  [KnownType(typeof(Occ600UIConfig))]
    public class Occ600UIConfig 
    { }

If so, why is the DCS throwing the following exception?

{"Error in line 1 position 387. Element 'http://schemas.microsoft.com/2003/10/Serialization/Arrays:Value' contains data of the 'http://schemas.datacontract.org/2004/07/OCC600.Infrastructure.Dictionary.BusinessEntities:Occ600UIConfig' data contract. The deserializer has no knowledge of any type that maps to this contract. Add the type corresponding to 'Occ600UIConfig' to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding it to the list of known types passed to DataContractSerializer."}

Answer 1

The KnownType attribute is used to define and "advertise" descendant classes of a base class that might also be used in a given context.

But your data class in WCF should be marked primarily with a [DataContract] attribute (and all members you want to include with a [DataMember] attribute):

[DataContract]
public class Occ600UIConfig 
{ }

If you don't have any inheritance hierarchies, you never need the KnownType attribute.