title: Where is the FocusManager in a uwp xaml applications?
body: <p>I'm trying to solve a problem in a xaml / uwp application. Most of the suggestions I'm finding refer to a class called FocusManager, which appears to be a property of many controls and containers.</p>
  
  <p>Unfortunately, whenever I try to use it, I find that there is no such property available in my application on any of my controls, including Page, UserControl, StackPanel, etc.</p>
  
  <p>I'm confused as to why this is.</p>
  
  <p>How do I access this class in my application? Or, is there a different way to change the focus?</p>