title: Removing and adding a pivot item in runtime doesn't work
body: <p>i am trying to add and remove a pivot item at runtime but it does not cause the layout to repaint itself so the removed pivot item still shows. If i add or remove a pivot item in the method OnNavigatedTo, it works. But i need this when the page is already "there", not in OnNavigatedTo. Any suggestions?</p>
  
  <p>Best
  Yimei </p>