Wcf service inheritance (Extend a service)

Question

The program I am working on exposes both callbacks and services using wcf. Basically, what the services do is simply return some variables value. As for the callback, they simply update those variables.

I want to be able to expose one class containing only the services and one class containing the services and the callbacks.

For example :

[ServiceContract]
[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceClass
{
  [OperationContract]
  public int getValue()
  {
    return mValue;
  }

  protected static int mValue;

};

[ServiceContract]
[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceAndCallbackClass : ServiceClass
{
  [OperationContract]
  public bool subscribe()
  {
    // some subscribing stuff
  }

  public void MyCallback()
  {
    ++mValue;

    // Notify every subscriber with the new value
  }

};

If I want only the services, I can use the base class. However, if I want to subscribe to the callback and use the service, I can use ServiceAndCallbackClass.

Is this possible ?

Answer 1

One solution I found :

Make 2 interfaces. The first one containing only the services and the second one inheriting from the first one and adding the callbacks.

An implementation class would implement the 2 interfaces.

Example :

[ServiceContract]
[ServiceKnownType(typeof(ICallback))]
public interface IService
{
  [OperationContract]
  int GetData();
}

[ServiceContract]
public interface ICallback : IService
{
  [OperationContract]
  public bool subscribe();
}

[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceClass : IService, ICallback
{
  public int getValue()
  {
    return mValue;
  }

  public bool subscribe()
  {
    // some subscribing stuff
  }

  public void myCallback()
  {
    ++mValue;

    // Notify every subscriber with the new value
  }    

  protected static int;
};

[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceAndCallbackClass : ServiceClass
{
  // Dummy implementation used to create second service
};

From there, we can create 2 services. One based on the implementation class and one based on the "Dummy" class. Each service would be created from a different interface and thus exposing different methods.