Revit.Plugln/FWindSoft/FWindSoft.Wpf/Themes/SpliterStyle.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:controls="clr-namespace:FWindSoft.Wpf.Controls">
    <Style  TargetType="{x:Type controls:LineSpliter}">
        <Setter Property="BorderBrush" Value="Black"></Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type controls:LineSpliter}">
                    <Border 
                        VerticalAlignment="Center" HorizontalAlignment="Stretch">
                        <Line X1="0" Y1="0"  X2="1" Y2="0" x:Name="Line" Stretch="Fill"   StrokeThickness="0.5" Stroke="{TemplateBinding BorderBrush}" ></Line>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="controls:LineSpliter.Orientation" Value="Vertical">
                            <Setter Property="X2" TargetName="Line" Value="0"></Setter>
                            <Setter Property="Y2" TargetName="Line" Value="1"></Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>