Stroke Start Line Cap

   
      
<Grid xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Grid.Resources>
        <Style TargetType="{x:Type TextBlock}">
            <Setter Property="FontSize" Value="16" />
            <Setter Property="Margin" Value="24" />
            <Setter Property="VerticalAlignment" Value="Center" />
        </Style>

        <Style TargetType="{x:Type Line}">
            <Setter Property="Grid.Column" Value="1" />
            <Setter Property="Y1" Value="3" />
            <Setter Property="X2" Value="400" />
            <Setter Property="Y2" Value="30" />
            <Setter Property="StrokeThickness" Value="25" />
            <Setter Property="Stroke" Value="Black" />
            <Setter Property="StrokeDashArray" Value="2 2 3 4" />

            <Setter Property="StrokeStartLineCap" Value="{Binding RelativeSource={RelativeSource self}, Path=StrokeDashCap}" />

            <Setter Property="StrokeEndLineCap" Value="{Binding RelativeSource={RelativeSource self}, Path=StrokeDashCap}" />

        </Style>
    </Grid.Resources>

    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>

    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="Auto" />
    </Grid.ColumnDefinitions>

    <!-- PenLineCap.Flat. -->
    <TextBlock Grid.Row="0" Text="PenLineCap.Flat" />
    <Line Grid.Row="0" />

    <!-- PenLineCap.Square. -->
    <TextBlock Grid.Row="1" Text="PenLineCap.Square" />
    <Line Grid.Row="1" StrokeDashCap="Square" />

    <!-- PenLineCap.Round. -->
    <TextBlock Grid.Row="2" Text="PenLineCap.Round" />
    <Line Grid.Row="2" StrokeDashCap="Round" />

    <!-- Triangle.Triangle. -->
    <TextBlock Grid.Row="3" Text="PenLineCap.Triangle" />
    <Line Grid.Row="3" StrokeDashCap="Triangle" />
</Grid>