What's the best way to serialize an array based on an interface in WCF?

Question

First the code:

[ServiceContract]
public interface IWorker
{
    [OperationContract]
    void Process(XmlElement data);
    [OperationContract]
    void Update(Rule rule);
}

[DataContract]
public class Rule
{
    [OperationContract]
    public string Expression { get; set; }
    [OperationContract]
    public List<IAction> Actions { get; set; }
}

public interface IAction
{
    void Execute(XmlElement data);
}

A dispatcher encodes data as xml and sends it to an IWorker instance where each expression is evaluated. When an IWorker instance evaluates an expression as true, IAction.Execute is called and the xml/data is passed.

What's the best way to serialize Rule.Actions? I've started writing a custom serializer but I'd prefer to see if there is an easier way.

Thanks.

Answer 1

I dont think you can use interfaces in DataContracts (someone correct me if im wrong, but i assume thats like trying to use a generic too). What I do, is have a parent class, then add the KnownType attribute. For instance

[DataContract]
public class Action
{
    //members and properties
}


[DataContract]
public class SomeOtherAction:Action
{
    //more implimentation
}

[DataContract]
[KnownType(typeof(SomeOtherAction))]
public class Rule
{
    [DataMember]
    List<Action> Actions{get;set;}

}

Now you can stuff any object that inherits from the parent Action object in to the Actions list, and it will properly serialize all their respective class properties (as long as the object is listed as a knowntype).

*I used "Action" name as an example to relate to yours, obviously Action is a keyword in .NET