如何使用border-image创建嵌入边框

Question

我正在尝试使用border-image为图像创建自定义边框，但需要插入边框而不是图像外部。

这是我现在所拥有的：https://jsfiddle.net/kq69nxvn/

<Window x:Class="ListBoxUpdate.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="ListBoxUpdate" Height="300" Width="300"
    >
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Grid Grid.Column="0">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>
            <Button Grid.Row="0" Content="Show items" Click="HandleButtonClick"/>
            <TextBlock Grid.Row="1" x:Name="textBlock" />
        </Grid>
        <ListBox
            x:Name="listBox"
            Grid.Column="1"
            ItemsSource="{Binding Strings}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBox 
                        Text="{Binding ., Mode=OneWay}"
                    LostFocus="HandleTextBoxLostFocus"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>
</Window>

提前致谢！