FocusVisualStyle
<Style x:Key="MyFocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Margin="-2" StrokeThickness="1" Stroke="Red" StrokeDashArray="1 2"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<StackPanel Background="Ivory" Orientation="Horizontal">
<Canvas Width="10"/>
<Button Width="100" Height="30" FocusVisualStyle="{DynamicResource MyFocusVisual}">
Focus Here</Button>
<Canvas Width="100"/>
<Button Width="100" Height="30" FocusVisualStyle="{DynamicResource MyFocusVisual}">
Focus Here</Button>
</StackPanel>
参考文章：
为控件中的焦点设置样式以及 FocusVisualStyle
