title: AutoComplete for a WPF editable ComboBox including Separator control shows System.Windows.Controls.Separator
body: <p>AutoComplete for a WPF editable ComboBox including Separator control shows System.Windows.Controls.Separator.</p>
  
  <p>With this xaml:</p>
  
  <pre><code>&lt;ComboBox IsEditable="true"&gt;
     &lt;ComboBoxItem Content="aaaaa"/&gt;
     &lt;ComboBoxItem Content="bbbbb"/&gt;
     &lt;ComboBoxItem Content="ccccc"/&gt;
  &lt;/ComboBox&gt;
  </code></pre>
  
  <p>Users can started typing with a to c, to auto complete the rest of characters.
  a will become aaaaa, b will become bbbbb and so on.</p>
  
  <p>However, the problem is if I want to add separator and make some of them exempting from auto-completion.
  I tried this one:</p>
  
  <pre><code>&lt;ComboBox IsEditable="true"&gt;
     &lt;ComboBoxItem Content="aaaaa"/&gt;
     &lt;ComboBoxItem Content="bbbbb"/&gt;
     &lt;Separator IsEnabled="false"/&gt;
     &lt;ComboBoxItem Content="ccccc" IsEnabled="false"/&gt;
  &lt;/ComboBox&gt;
  </code></pre>
  
  <p>When I hit c, combobox still show ccccc as choice. 
  Also, when I hit S, weirdly the combobox shows System.Windows.Controls.Separator as a choice(!)</p>
  
  <p>My expectation was auto complete only supports typing a and b since the other two (Separator and ccccc) is set to IsEnabled="false".</p>
  
  <p>Is there any solution for this?
  Please let me know.</p>