Checker brush

<Window x:Class="CheckerBackground.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Checker Background"
        Width="525"
        Height="350">

    <Window.Resources>
        <SolidColorBrush x:Key="DarkSquareColor" Color="#18FFFFFF" />
        <SolidColorBrush x:Key="LightSquareColor" Color="#34FFFFFF" />
        <DrawingBrush x:Key="CheckerBackground"
                      Stretch="None"
                      TileMode="Tile"
                      Viewport="0,0,20,20"
                      ViewportUnits="Absolute">
            <DrawingBrush.Drawing>
                <DrawingGroup>
                    <GeometryDrawing Brush="{StaticResource DarkSquareColor}">
                        <GeometryDrawing.Geometry>
                            <GeometryGroup>
                                <RectangleGeometry Rect="0,0,10,10" />
                                <RectangleGeometry Rect="10,10,10,10" />
                            </GeometryGroup>
                        </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                    <GeometryDrawing Brush="{StaticResource LightSquareColor}">
                        <GeometryDrawing.Geometry>
                            <GeometryGroup>
                                <RectangleGeometry Rect="10,0,10,10" />
                                <RectangleGeometry Rect="0,10,10,10" />
                            </GeometryGroup>
                        </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                </DrawingGroup>
            </DrawingBrush.Drawing>
        </DrawingBrush>
    </Window.Resources>

    <Grid>
        <Rectangle Fill="#FF000000" />
        <Rectangle Fill="{DynamicResource CheckerBackground}" />
    </Grid>
</Window>