title: wpf combobox display 1st item from list
body: <p>i have a combobox bound to an ObservableCollection:-</p>
  
  <pre><code>&lt;ComboBox Name="combo" ItemsSource="{Binding Things}" SelectionChanged="ComboBox_SelectionChanged" &gt;
  </code></pre>
  
  <p>in the code behind I have</p>
  
  <pre><code>Dim thingArray = New ObservableCollection(Of Things)   
  Me.combo.DataContext = Me.thingArray
  </code></pre>
  
  <p>Assume thingArray is initialized to 5 <code>Thing</code> objects and <code>Thing</code> has a <code>toString()</code> implementation. I want to display the first item <code>Thing(0)</code> by default on the ComboBox. How do i do that?</p>