Semi.Avalonia/demo/Semi.Avalonia.Demo/Pages/ThemeVariantDemo.axaml

<UserControl
    x:Class="Semi.Avalonia.Demo.Pages.ThemeVariantDemo"
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:vm="clr-namespace:Semi.Avalonia.Demo.Pages"
    x:DataType="vm:ThemeVariantDemoViewModel"
    d:DesignHeight="450"
    d:DesignWidth="800"
    mc:Ignorable="d">
    <Design.DataContext>
        <vm:ThemeVariantDemoViewModel />
    </Design.DataContext>
    <StackPanel>
        <Border Theme="{StaticResource CardBorder}">
            <StackPanel>
                <ListBox
                    Theme="{StaticResource CardRadioGroupListBox}"
                    ItemsSource="{Binding ThemeVariants}"
                    SelectedItem="{Binding SelectedThemeVariant}" />
                <DatePicker />
                <CalendarDatePicker />
            </StackPanel>
        </Border>
        <ThemeVariantScope RequestedThemeVariant="{Binding SelectedThemeVariant}">
            <Border Theme="{StaticResource CardBorder}">
                <StackPanel>
                    <ListBox
                        Theme="{StaticResource CardRadioGroupListBox}"
                        ItemsSource="{Binding ThemeVariants}"
                        SelectedItem="{Binding SelectedThemeVariant}" />
                    <DatePicker />
                    <CalendarDatePicker />
                </StackPanel>
            </Border>
        </ThemeVariantScope>
    </StackPanel>
</UserControl>