Avalonia/samples/ControlCatalog/Pages/SplitViewPage.xaml

<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"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:Class="ControlCatalog.Pages.SplitViewPage">

  <Border>

    <Grid ColumnDefinitions="*,225">

      <StackPanel Grid.Column="1" Orientation="Vertical" Spacing="4" Margin="5">
        <ToggleButton Name="PaneOpenButton"
                      Content="IsPaneOpen"
                      IsChecked="{Binding IsPaneOpen, ElementName=SplitView}" />

        <ToggleButton Name="UseLightDismissOverlayModeButton"
                      Content="UseLightDismissOverlayMode"
                      IsChecked="{Binding UseLightDismissOverlayMode, ElementName=SplitView}" />

        <ToggleSwitch OffContent="Left" OnContent="Right" Content="Placement" IsChecked="{Binding !IsLeft}" />

        <TextBlock Text="DisplayMode" />
        <ComboBox Name="DisplayModeSelector" Width="170" Margin="10" SelectedIndex="{Binding DisplayMode}">
          <ComboBoxItem>Inline</ComboBoxItem>
          <ComboBoxItem>CompactInline</ComboBoxItem>
          <ComboBoxItem>Overlay</ComboBoxItem>
          <ComboBoxItem>CompactOverlay</ComboBoxItem>
        </ComboBox>

        <TextBlock Text="PaneBackground" />
        <ComboBox Name="PaneBackgroundSelector" SelectedIndex="0" Width="170" Margin="10">
          <ComboBoxItem Tag="{DynamicResource SystemControlBackgroundChromeMediumLowBrush}">SystemControlBackgroundChromeMediumLowBrush</ComboBoxItem>
          <ComboBoxItem Tag="Red">Red</ComboBoxItem>
          <ComboBoxItem Tag="Blue">Blue</ComboBoxItem>
          <ComboBoxItem Tag="Green">Green</ComboBoxItem>
        </ComboBox>

        <TextBlock Text="{Binding Value, ElementName=OpenPaneLengthSlider, StringFormat='{}OpenPaneLength: {0}'}" />
        <Slider Name="OpenPaneLengthSlider" Value="256" Minimum="128" Maximum="500"
                Width="150" />

        <TextBlock Text="{Binding Value, ElementName=CompactPaneLengthSlider, StringFormat='{}CompactPaneLength: {0}'}" />
        <Slider Name="CompactPaneLengthSlider" Value="48" Minimum="24" Maximum="128"
                Width="150" />

      </StackPanel>

      <Border BorderBrush="{DynamicResource SystemControlHighlightBaseLowBrush}"
            BorderThickness="1">
        <!--{Binding SelectedItem.Tag, ElementName=PaneBackgroundSelector}-->
        <SplitView Name="SplitView"
                      PanePlacement="{Binding PanePlacement}"
                      PaneBackground="{Binding SelectedItem.Tag, ElementName=PaneBackgroundSelector}"
                      OpenPaneLength="{Binding Value, ElementName=OpenPaneLengthSlider}"
                      CompactPaneLength="{Binding Value, ElementName=CompactPaneLengthSlider}"
                      DisplayMode="{Binding CurrentDisplayMode}">
          <SplitView.Pane>
            <Grid>
              <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
                <RowDefinition Height="Auto" />
              </Grid.RowDefinitions>
              <TextBlock Text="PANE CONTENT" FontWeight="Bold" Name="PaneHeader" Margin="5,12,0,0" />
              <ComboBox Width="150" Grid.Row="1">
                <ComboBoxItem Content="Item1"/>
                <ComboBoxItem Content="Item2"/>
                <ComboBoxItem Content="Item3"/>
              </ComboBox>
              <ListBoxItem Grid.Row="2" VerticalAlignment="Top" Margin="0 10">
                <StackPanel Orientation="Horizontal">
                  <!--Path glyph from materialdesignicons.com-->
                  <Border Width="48">
                    <Viewbox Width="24" Height="24" HorizontalAlignment="Left">
                      <Canvas Width="24" Height="24">
                        <Path Fill="{DynamicResource SystemControlForegroundBaseHighBrush}" Data="M16 17V19H2V17S2 13 9 13 16 17 16 17M12.5 7.5A3.5 3.5 0 1 0 9 11A3.5 3.5 0 0 0 12.5 7.5M15.94 13A5.32 5.32 0 0 1 18 17V19H22V17S22 13.37 15.94 13M15 4A3.39 3.39 0 0 0 13.07 4.59A5 5 0 0 1 13.07 10.41A3.39 3.39 0 0 0 15 11A3.5 3.5 0 0 0 15 4Z" />
                      </Canvas>
                    </Viewbox>
                  </Border>
                  <TextBlock Text="People" VerticalAlignment="Center" />
                </StackPanel>
              </ListBoxItem>
              <TextBlock Grid.Row="3" Text="Item at bottom" Margin="60,12" />
            </Grid>
          </SplitView.Pane>

          <Grid>
            <TextBlock FontSize="14" FontWeight="700" Text="SplitViewContent" HorizontalAlignment="Center" VerticalAlignment="Center"  Foreground="{DynamicResource SystemControlForegroundBaseHighBrush}" />
            <TextBlock FontSize="14" FontWeight="700" Text="SplitViewContent" TextAlignment="Left"  Foreground="{DynamicResource SystemControlForegroundBaseHighBrush}" />
            <TextBlock FontSize="14" FontWeight="700" Text="SplitViewContent" HorizontalAlignment="Right" TextAlignment="Left"  Foreground="{DynamicResource SystemControlForegroundBaseHighBrush}" />
            <TextBlock FontSize="14" FontWeight="700" Text="SplitViewContent" VerticalAlignment="Bottom" TextAlignment="Left"  Foreground="{DynamicResource SystemControlForegroundBaseHighBrush}" />
            <TextBlock FontSize="14" FontWeight="700" Text="SplitViewContent" VerticalAlignment="Bottom" HorizontalAlignment="Right" TextAlignment="Left"  Foreground="{DynamicResource SystemControlForegroundBaseHighBrush}" />
          </Grid>

        </SplitView>
      </Border>
      
    </Grid>
  </Border>

</UserControl>