title: WP7: Understanding dark / light icons and how to change dynamically depending on thems (via mvvmlight)?
body: <p>From what I understand is that there is 2 themes in wp7, light and dark. I notice the application bar has generic images, they change to light or dark automatically.</p>
  
  <p>But I placed a image from the SDK icons directory onto xml screen, I noticed they have 2 variants, light or dark. </p>
  
  <p>Problem is that when I view the page with dark or light, the application bar buttons change according to the theme but the image doesn't.</p>
  
  <p>Am I doing this right?</p>
  
  <p>So do I have to check for a event change or something? So I know the theme has changed to automatically update the image from light to dark (or dark to light).</p>
  
  <p>If this is the case, I am using mvvmlight and have my code behind quite clean, is this possible to do within the viewmodel or must it take place in the app.xaml?</p>