title: Check if a ComboBox Contains Item
body: <p>I have this:</p>
  
  <pre><code>&lt;ComboBox SelectedValuePath="Content" x:Name="cb"&gt;
    &lt;ComboBoxItem&gt;Combo&lt;/ComboBoxItem&gt;
    &lt;ComboBoxItem&gt;Box&lt;/ComboBoxItem&gt;
    &lt;ComboBoxItem&gt;Item&lt;/ComboBoxItem&gt;
  &lt;/ComboBox&gt;
  </code></pre>
  
  <p>If I use</p>
  
  <pre><code>cb.Items.Contains("Combo")
  </code></pre>
  
  <p>or</p>
  
  <pre><code>cb.Items.Contains(new ComboBoxItem {Content = "Combo"})
  </code></pre>
  
  <p>it returns <code>False</code>.</p>
  
  <p>Can anyone tell me how do I check if a <code>ComboBoxItem</code> named <code>Combo</code> exists in the <code>ComboBox</code> <code>cb</code>?</p>