title: Cannot find Region in RegionManager (using PRISM)
body: <p>I'm writing an application in Prism. I have a user control and contains two <code>&lt;ContentControl&gt;</code> controls. These both have Regions assigned to them. The usercontrol is being hosted in a <code>Window</code> that is being shown using <code>ShowDialog()</code>.<br>
  I'm adding the one of my views to a region using view discovery and the other I want to inject the view into its region. The view discovery works fine. However when I try and reference the other region to inject the view I get the exception:</p>
  
  <p><strong>KeyNotFoundException</strong><br>
  The region manager does not contain the <em>MyRegion</em> region.</p>
  
  <p>When I look in the RegionManagers regions neither the one that I'm trying to inject the view exists or the one being that's using view discovery.</p>
  
  <p>Does it matter that I'm in a different window to the Shell? I thought there was only one RegionManager, but there must be two for my view discovery to still be working...? Or is it because I have two new regions being created later in the applications life cycle? Or is it because the new regions aren't inside the my MainRegion?</p>
  
  <p><strong>EDIT:</strong><br>
  After doing some digging it looks like the Region is created but it can't find an instance of the RegionManager so it doesn't get added. Any clues?</p>