title: SelectedItem in ObservableCollection
body: <p>I have: </p>
  
  <pre><code>&lt;DataTemplate x:Name="_ComboBoxTemplate" x:Key="_ComboBoxTemplate"&gt;
      &lt;StackPanel Orientation="Horizontal"&gt;
          &lt;StackPanel&gt;
              &lt;StackPanel Orientation="Horizontal" HorizontalAlignment="Center"&gt;
                  &lt;TextBlock VerticalAlignment="Center" Text="{Binding}" FontSize="24"/&gt;
              &lt;/StackPanel&gt;
          &lt;/StackPanel&gt;
      &lt;/StackPanel&gt;
  &lt;/DataTemplate&gt;
  
  &lt;ComboBox x:Name="_criteria" ItemTemplate="{StaticResource _ComboBoxTemplate}" ItemsSource="{Binding}"/&gt;
  </code></pre>
  
  <p>In the code behind:</p>
  
  <pre><code>this.DataContext = new string[] { "0", "1", "2", "3", "4", "5" };
  </code></pre>
  
  <p>How do I get it so that the default <code>SelectedItem</code> in <code>ComboBox</code> is <code>5</code>?</p>