MainWindow.xaml

<Window x:Class="FocusVisualStyle.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:FocusVisualStyle"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Window.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>
    </Window.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>
</Window>