aistudio-wpf-diagram/AIStudio.Wpf.DiagramDesigner/Controls/BlockItemsControl.xaml

<ItemsControl x:Class="AIStudio.Wpf.DiagramDesigner.BlockItemsControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:AIStudio.Wpf.DiagramDesigner"
             xmlns:dd="clr-namespace:AIStudio.Wpf.DiagramDesigner"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
    <ItemsControl.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBoxItem}">
                        <dd:BlockBorder 
                            dd:WidthAndHeightProps.Active="True"
                            dd:WidthAndHeightProps.BoundActualWidth="{Binding ActualItemWidth,Mode=OneWayToSource}"
                            dd:WidthAndHeightProps.BoundActualHeight="{Binding ActualItemHeight,Mode=OneWayToSource}">
                            <ContentControl Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}"/>
                        </dd:BlockBorder>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </ItemsControl.ItemContainerStyle>
</ItemsControl>