Flow.Launcher/Flow.Launcher/Resources/Controls/CardGroup.xaml

<UserControl x:Class="Flow.Launcher.Resources.Controls.CardGroup"
             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:cc="clr-namespace:Flow.Launcher.Resources.Controls"
             mc:Ignorable="d"
             d:DataContext="{d:DesignInstance cc:CardGroup}"
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Resources>
        <Style TargetType="cc:Card" x:Key="FirstStyle">
            <Setter Property="cc:CardGroup.Position" Value="First" />
        </Style>
        <Style TargetType="cc:Card" x:Key="MiddleStyle">
            <Setter Property="cc:CardGroup.Position" Value="Middle" />
        </Style>
        <Style TargetType="cc:Card" x:Key="LastStyle">
            <Setter Property="cc:CardGroup.Position" Value="Last" />
        </Style>

        <cc:CardGroupCardStyleSelector
            x:Key="CardStyleSelector"
            FirstStyle="{StaticResource FirstStyle}"
            MiddleStyle="{StaticResource MiddleStyle}"
            LastStyle="{StaticResource LastStyle}" />
    </UserControl.Resources>
    <Border Background="{DynamicResource Color00B}" BorderBrush="{DynamicResource Color03B}" BorderThickness="1"
            CornerRadius="5">
        <ItemsControl ItemsSource="{Binding Content, RelativeSource={RelativeSource AncestorType=cc:CardGroup}}"
                      ItemContainerStyleSelector="{StaticResource CardStyleSelector}" />
    </Border>
</UserControl>