title: WPF: ComboBox only refreshes to binding when never opened
body: <p>I have a combobox and set the itemssource to a list of strings: </p>
  
  <pre><code>private List&lt;string&gt; list = new List&lt;string&gt;();
  ...
  ComboBox cbo = new ComboBox();
  cbo.ItemsSource = list;
  </code></pre>
  
  <p>The combobox gets filled successful on startup.<br>
  But when the list is changed, the combobox doesn't update its items, BUT only when I expanded the items before, else the combobox gets updated...<br>
  Also weird: when I trace the count of items of the combobox, the count is the correct updated number, but the displayed items aren't.<br>
  Somebody has an idea, what's going on here?</p>
  
  <p>EDIT: See solution in comments to post of Robert</p>