title: How to switch between document tabs in AvalonDock 2
body: <p>I have build a little app that uses AvalonDock 2.  I bound my view models to the docking manager, can create and remove documents, all fine.  However, there is one thing I do net get to work:  When I have multiple documents open I am not able to make a specific document tab the active and visible tab (like if I would click on the tab header) from code.</p>
  
  <p>I have bound to the "ActiveContent" property and set it to the document I want to be the active and visible one, but that does not help.</p>
  
  <p>Can please someone give me some advice on how to do that?</p>