Avalonia/samples/ControlCatalog/Views/NotificationView.xaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ControlCatalog.Views.NotificationView">
    <Border Padding="12" MinHeight="20" Background="#FF444444">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <ContentControl Margin="0,0,12,0" Width="25" Height="25" VerticalAlignment="Top">
                <TextBlock Text="&#xE115;" FontFamily="Segoe UI Symbol" FontSize="20" TextAlignment="Center" VerticalAlignment="Center"/>
            </ContentControl>
            <DockPanel Grid.Column="1">
                <TextBlock DockPanel.Dock="Top" Text="{Binding Title}" FontWeight="Medium" />
                <DockPanel LastChildFill="False" DockPanel.Dock="Bottom" Margin="0,8,0,0">
                    <Button x:Name="Ok" Content="Ok" DockPanel.Dock="Right"  />
                    <Button x:Name="Cancel" Content="Cancel" DockPanel.Dock="Right" Margin="0,0,8,0" />
                </DockPanel>
                <TextBlock Text="{Binding Message}" TextWrapping="Wrap" Opacity=".8" Margin="0,8,0,0"/>
            </DockPanel>
        </Grid>
    </Border>
</UserControl>