title: How to change ComboBox's Background Property during Mouse Hover
body: <p>I have a Rounded Border containing a ComboBox as follow:</p>
  
  <p><img src="https://i.stack.imgur.com/8Usn4.png" alt="enter image description here"></p>
  
  <p>As soon as my mouse hover on the ComboBox, I get this</p>
  
  <p><img src="https://i.stack.imgur.com/Iz3kV.png" alt="enter image description here"></p>
  
  <p>I want to get rid of the button-like background. I tried setting background to white or null in <strong>MouseEnter</strong>, <strong>MouseLeave</strong>, <strong>MouseUp</strong>... everything with Mouse but still I can't get rid of the default button background on the ComboBox. Does anyone has a clue?</p>
  
  <p>Code below:</p>
  
  <pre><code>/* XAML */
  &lt;Border CornerRadius="11" BorderThickness="1" Height="24" Width="70" 
      Grid.Column="1" Margin="5,5,5,5" VerticalAlignment="Center" 
      HorizontalAlignment="Left" Background="White"&gt;
      &lt;ComboBox x:Name="comboBox1" BorderBrush="{x:Null}" 
            Background="{x:Null}" Width="70" MouseMove="MouseHover"
            MouseEnter="MouseHover"
      &lt;/ComboBox&gt;
      &lt;/Border&gt;
  
  /* C# code */
  private void MouseHover(object sender, RoutedEventArgs e)
  {
      comboBox1.Background = null;
  }
  </code></pre>