title: ViewModel event fires multiple times
body: <p>I'm using MVVM Light for my application and I have also implemented the INavigationService for going back/for between pages.</p>
  
  <p>So in a common scenario, it's like this</p>
  
  <p>MainPage > Categories > Rounds > DataPage.</p>
  
  <p>In the DataPage, I'm making a request to fetch the results and depending on the result returned from the callback I call the .GoBack() method to pop the current page from the stack and return to Rounds.</p>
  
  <p>What I have noticed is that if I hit first the DataPage and the .GoBack() gets called and then tap on a different round the callback method will be fired twice, and if I go back and in again thrice, and continues like this.</p>
  
  <p>Essentially this means that the .GoBack() will be called again and the navigation gets messed up.</p>
  
  <p>I believe this has to do with not cleaning up the previous VM's, I tried changing this behavior with the UnRegister / Register class from SimpleIOC but no luck.</p>