title: Show ToolTip of disabled and read-only Combobox
body: <p>I am currently facing the problem that my disbaled <code>ComboBox</code>, which does have a tooltip won't show when I am hovering it with my mouse. The tooltip shows correctly when the <code>ComboBox</code> is not disabled.</p>
  
  <p>The code of the <code>ComboBox</code> is:</p>
  
  <pre><code>&lt;ComboBox ItemsSource="{Binding AvailableItems}" 
            SelectedValue="{Binding Item, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}"
            IsReadOnly="{Binding IsDeletable, Converter={StaticResource BooleanInverter}}"
            IsEnabled="{Binding IsDeletable}" 
            IsHitTestVisible="{Binding IsDeletable}" 
            ToolTip="{Binding Item.ConcatenatedNameInterchanged}" 
            ToolTipService.ShowOnDisabled="True" /&gt;
  </code></pre>
  
  <p>The bound values are:</p>
  
  <ul>
  <li><code>IsReadOnly = True</code></li>
  <li><code>IsEnabled = False</code></li>
  <li><code>IsHitTestVisible = False</code></li>
  <li><code>ToolTip = "Lorem ipsum dolor sit amet."</code></li>
  </ul>
  
  <p>I have tried to:</p>
  
  <ul>
  <li>set <a href="https://msdn.microsoft.com/en-US/library/system.windows.controls.tooltipservice.showondisabled" rel="nofollow noreferrer"><code>ToolTipService.ShowOnDisabled</code></a> in the default style, without success.</li>
  <li>hard-code <code>IsHitTestVisible="True"</code>, without success.</li>
  </ul>
  
  <p>Do you have any ideas? Thanks in advance!</p>