[C#/WPF] Binding 태그 확장 : RelativeSource 속성에서 RelativeSource 태그 확장을 사용해 엘리먼트 자신의 속성 바인딩하기

<Canvas
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Canvas.Resources>
        <Style x:Key="BaseStyleKey" TargetType="{x:Type Line}">
            <Setter Property="Stroke" Value="Blue" />
        </Style>
        <Style x:Key="HorizontalStyleKey" TargetType="{x:Type Line}" BasedOn="{StaticResource BaseStyleKey}">
            <Setter Property="X1" Value="100" />
            <Setter Property="X2" Value="300" />
            <Setter Property="Y2" Value="{Binding RelativeSource={RelativeSource self}, Path=Y1}" />
        </Style>
        <Style x:Key="VerticalStyleKey" TargetType="{x:Type Line}" BasedOn="{StaticResource BaseStyleKey}">
            <Setter Property="Y1" Value="100" />
            <Setter Property="Y2" Value="300" />
            <Setter Property="X2" Value="{Binding RelativeSource={RelativeSource self}, Path=X1}" />
        </Style>
    </Canvas.Resources>
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="100" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="125" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="150" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="175" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="200" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="225" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="250" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="275" />
    <Line Style="{StaticResource HorizontalStyleKey}" Y1="300" />

    <Line Style="{StaticResource VerticalStyleKey}" X1="100" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="125" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="150" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="175" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="200" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="225" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="250" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="275" />
    <Line Style="{StaticResource VerticalStyleKey}" X1="300" />
</Canvas>