Navigate away method thtas call on the controller

Question

On my page I have a link to a event handler linked to a singleton class which notifies me of updates to the data. When I navigate a way and come back to the page I then receive 2 notifications which I know related to the event methods has now been registered twice. I have attempted to override the dispose class so that when I navigate away I deregister then event methods, but the dispose methods never hits.
What do I need to link to so that I can deregister from the delegate so that when I naviagte back to the page it will reregister and I only get 1 message