ShrlAlgoToolkit/WPFluent/Resources/DefaultControlFocusVisualStyle.xaml

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

    <Style x:Key="DefaultControlFocusVisualStyle">
        <Setter Property="Control.Template">
            <Setter.Value>
                <ControlTemplate>
                    <Rectangle
                        RadiusX="4"
                        RadiusY="4"
                        SnapsToDevicePixels="True"
                        Stroke="{DynamicResource KeyboardFocusBorderColorBrush}"
                        StrokeThickness="1" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style x:Key="{x:Static SystemParameters.FocusVisualStyleKey}" BasedOn="{StaticResource DefaultControlFocusVisualStyle}" />

</ResourceDictionary>