Data Contract Hierarchy
Your data contract class may be a subclass of another data contract class. WCF requires that
every level in the class hierarchy explicitly opt in for a given data
contract, because the DataContract
attribute
is not inheritable:
[DataContract]
class Contact
{
[DataMember]
public string FirstName;
[DataMember]
public string LastName;
}
[DataContract]
class Customer : Contact
{
[DataMember]
public int CustomerNumber;
}
Failing to designate every level in the class hierarchy as
serializable or as a data contract will result in an InvalidDataContractException
at the service
load time. WCF lets you mix the Serializable
and
DataContract
attributes in the class
hierarchy:
[Serializable] class Contact {...} [DataContract] class Customer : Contact {...}
However, the Serializable
attribute will typically be at the root of the class hierarchy, if it
appears at all, because new classes should use the DataContract
attribute.
When you export a data contract hierarchy, the metadata maintains the
hierarchy, and all levels of the class hierarchy are exported when you
make use of the subclass in a service contract:
[ServiceContract] interface IContactManager { [OperationContract] void AddCustomer(Customer customer); //Contact is exported as well ... }
Known Types
In traditional object-oriented programming, a reference to a subclass is also a reference to its base class, so the subclass maintains an Is-A relationship with its base class. Any method that expects a reference to a base ...
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