title: How do you change Background for a Button MouseOver in WPF?
body: <p>I have a button on my page with this XAML:</p>
  
  <pre><code>&lt;Button Content="Button" HorizontalAlignment="Left" VerticalAlignment="Bottom" 
      Width="50" Height="50" HorizontalContentAlignment="Left" 
      BorderBrush="{x:Null}" Foreground="{x:Null}" Margin="50,0,0,0"&gt;
      &lt;Button.Style&gt;
          &lt;Style TargetType="Button"&gt;
              &lt;Setter Property="Background" Value="Green"/&gt;
              &lt;Style.Triggers&gt;
                  &lt;Trigger Property="IsMouseOver" Value="True"&gt;
                      &lt;Setter Property="Background" Value="Red"/&gt;
                  &lt;/Trigger&gt;
              &lt;/Style.Triggers&gt;
          &lt;/Style&gt;
      &lt;/Button.Style&gt;
  &lt;/Button&gt;
  </code></pre>
  
  <p>But when I put mouse over my button, button's background changes to default windows gray background.<br>What's The Problem?<br></p>
  
  <p>This is the button picture before and after mouseover:<br>
  Before:<br><img src="https://i.stack.imgur.com/9n8RM.png" alt="Before"><br>
  After:<br><img src="https://i.stack.imgur.com/swHbJ.png" alt="After">
  <br></p>