title: PRISM + WPF - how to make region appear with animation?
body: <p>I have a WPF application written using PRISM architecture (MVVM).</p>
  
  <p>I have a 'Filters' <strong>Button</strong> at the top of the 'Main Window' region and a <strong>ListView</strong> with rows in it, looks like this :</p>
  
  <p><img src="https://s15.postimage.org/v8mgjupyx/img1.png" alt="before"></p>
  
  <p>I would like that when the 'Filters' button is pressed, a user-control will 'slide' (using animation) under the 'Filters' button and reveal itself, pushing the <strong>ListView</strong> and shrinking it ...</p>
  
  <p>It should look like this when the user-control finishes to appear :</p>
  
  <p><img src="https://s8.postimage.org/v7p5dh26r/img2.png" alt="after"></p>
  
  <p>The control that appears will have a 'hide' button that will fire an animation the shrinks it back to the top till it's gone ...</p>
  
  <p>How can I do this in PRISM ? Do I have to select a region for the user-control that appears ?</p>
  
  <p>How do I tell the region to 'show' itself using animation ?</p>