Based on what i said on the client side you would need to handle the unregister request here too, where you don't need to register an active operation, since it should just reuse the one from here. You probably could use some combination of the NotificationHandlerProxy and CompletedCallback to track the registration/unregistration of the handler. The operation-id is available using the ManagementRequestContext. Unfortunately this APIs are only half finished and a bit clumsy in cases...