title: Hide wpf popup when click on a Winform control
body: <p>I have an <code>ElementHost</code> object in a WinForm dialog. 
  This elementhosts child is a <code>Popup</code>. 
  I want to hide or close the <code>Popup</code> when the user clicks anywhere. I can do it when the click happened in the <code>Popup</code>. How to close it when the user clicks outside the popup, on a WinForm control?</p>