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;

        }

    }