Avalonia/samples/VirtualizationDemo/Views/ChatPageView.axaml

<UserControl 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="using:VirtualizationDemo.ViewModels"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:Class="VirtualizationDemo.Views.ChatPageView"
             x:DataType="vm:ChatPageViewModel">
  <ListBox ItemsSource="{Binding Messages}">
    <ListBox.ItemContainerTheme>
      <ControlTheme TargetType="ListBoxItem" BasedOn="{StaticResource {x:Type ListBoxItem}}">
        <Setter Property="Padding" Value="8"/>
      </ControlTheme>
    </ListBox.ItemContainerTheme>
    <ListBox.ItemTemplate>
      <DataTemplate>
        <Border CornerRadius="8" 
                Background="{DynamicResource SystemControlBackgroundAltHighBrush}"
                TextElement.Foreground="{DynamicResource SystemControlForegroundBaseHighBrush}"
                Padding="6"
                HorizontalAlignment="Left"
                MaxWidth="280">
          <DockPanel>
            <TextBlock DockPanel.Dock="Top"
                       Text="{Binding Sender}"
                       FontWeight="Bold"/>
            <TextBlock DockPanel.Dock="Bottom" 
                       Text="{Binding Timestamp}"
                       FontSize="10"
                       Foreground="{DynamicResource SystemControlForegroundBaseMediumBrush}"
                       TextAlignment="Right"
                       Margin="0 4 0 0"/>
            <TextBlock Text="{Binding Message}" TextWrapping="Wrap"/>
          </DockPanel>
        </Border>
      </DataTemplate>
    </ListBox.ItemTemplate>
  </ListBox>
</UserControl>