tab 默认虚线框处理

http://msdn.microsoft.com/en-us/library/ms744790(v=vs.110).aspx

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
  <Page.Resources>
    <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>
  </Page.Resources>
  <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>
</Page>