title: Understanding WPF - store Data in Model or ViewModel
body: <p>I am unsure where to store Data in a WPF Application. There are two principles that might collide. Could somebody please clear this up?  </p>
  
  <p>Principle 1: Data should be stored in the Model.<br>
  It follows, that for example an <code>ObservableCollection&lt;string&gt; Articles</code> should be stored in the Model. A Property in the ViewModel could make it available to the View.</p>
  
  <p>Principle 2: States relying on the View should be stored in the ViewModel.<br>
  That means that the <code>string _SelectedArticle</code> variable with corresponding Property <code>string SelectedArticle</code> should be stored in the ViewModel.  </p>
  
  <p>So far, I've put only Methods or values that don't affect the View into the Model, because I (maybe too) strongly followed principle 2. But I'm not sure if this is the right approach.</p>
  
  <p>Should I really keep some Data in the Model and some in the ViewModel or is there a place to store all the data?</p>