Data Contract Hierarchy in WCF

Data contract class may be the subclass of another data contract class.
Known Types
By default, you cannot use a subclass of a data contract class instead of its base class. The KnownType attribute allows you to designate acceptable subclasses for the data contract.

[DataContract]
[KnownType(typeof(Customer))]
class Contact
{...}

[DataContract]
class Customer : Contact
{...}

Service Known Types


Instead of using the KnownType attribute on the base data contract, when the ServiceKnownType attribute is applied on a specific operation on the service side, then only that operation (across all supporting services) can accept the known subclass.


When the ServiceKnownType attribute is applied at the contract level, all the operations on that contract can accept the known subclass across all implementing services

[ServiceContract]
[ServiceKnownType(typeof(Customer))]
interface IContactManager
{
   [OperationContract]
   void AddContact(Contact contact);

   [OperationContract]
   Contact[] GetContacts( );
}

Configuring Known Types


WCF also lets you configure the known types in the service's or client's config file.

Generics


You cannot define WCF contracts that rely on generic type parameters. Generics are specific to .NET, and using them would violate the service-oriented nature of WCF. However, you can use bounded generic types in your data contracts.