title: WPF Popup with rounded corners at the bottom only
body: <p>I wonder if it is possible to apply rounded corner to WPF popup bottom corners only. </p>
  
  <p>I know it is possible to apply rounded corners to all WPF popup corners, for example, <a href="https://social.msdn.microsoft.com/Forums/vstudio/en-US/0f6ec090-54f8-44bf-991b-94a049934a65/rounded-corner-popup?forum=wpf" rel="nofollow noreferrer">this</a>, but to only ones I am not sure. So is it possible? if so, could you provide a little example?</p>