title: WPF Application Update event
body: <p>In our developing app we have a 3d scene that contains our custom 3d objects.</p>
  
  <p>Those objects need to have their Update function to get called each frame in order to update its internals like physics, logics and visual animation step</p>
  
  <p>What would be a proper way to call this update queue each frame before the Window Content Rendered event is raised?</p>
  
  <p>To be more clear I'm looking for something like</p>
  
  <pre><code>void ApplicationUpdateEvent(float time_delta)
  {
     myObjectList.Update(float time_delta)
  }
  </code></pre>
  
  <p>P.S. I know we can call it in the Window.ContentRendered event handler too, but we want to avoid it since wpf can implicitly raise ContentRendered event, for example, if one calls win32 MessageBox function somewhere in the code of other events handlers</p>