public class DerivedFactory : ServiceHostFactory 
{ 

    protected override ServiceHost CreateServiceHost( Type t, Uri[] baseAddresses ) 
    { 
        return new DerivedHost( t, baseAddresses ); 
    }

    //Then in the CreateServiceHost method, we can do all of the
    //things that we can do in a self-hosted case:
    public override ServiceHostBase CreateServiceHost
            (string service, Uri[] baseAddresses)

    {

        // The service parameter is ignored here because we know our service.
        ServiceHost serviceHost = new ServiceHost(typeof(HelloService),
            baseAddresses);
        return serviceHost;
    }
}