Question

My goal is to load an external class in a running application environment (like a plugin model). Creating an instances of the class in an running environment is not the problem (the classes using an Interface). The problem is to get the class which must be available from a central WCF services.

Is it possible to transport an class or assembly to the client by using WCF?

Something like this:

[ServiceContract]
public interface ISourceData
{
    [OperationContract]
    xxx GetClassData { get; set; }  // <-- here to get data the class to app can create an instances of this
}

I hope that you understand my situation. Thanks.

Answer 1

First of all, the attribute in your sample above must be OperationContract, not DataContract. The DataContract attribute is for the class that you want to return in GetClassData.

The problem in your situation is that on the client side the class itself is not replicated when you add the service reference, but a stub is generated for the properties that you define in your DataContract. So you get the data, but not the logic.

You could now create an assembly which defines the data classes to be exchanged and add them to both the service and the client, but as I understand your question, you want to dynamically load assemblies in the service and send these “implementations” to the client without the client actually having access to the DLL that implements the class. This may not be possible in an easy way.

EDIT
Re-reading your question I now understand that you do not want to “transfer an instance”, but you want to transfer the class definition. One way would be to actually transfer the source code for the class and try to use Reflection.Emit to create a dynamic assembly. A sample of this can be found here.