Ursa.Avalonia/demo/Ursa.Demo/Pages/AnchorDemo.axaml

<UserControl
    x:Class="Ursa.Demo.Pages.AnchorDemo"
    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:u="https://irihi.tech/ursa"
    xmlns:viewModels="clr-namespace:Ursa.Demo.ViewModels"
    d:DesignHeight="450"
    d:DesignWidth="800"
    x:DataType="viewModels:AnchorDemoViewModel"
    mc:Ignorable="d">
    <TabControl>
        <TabItem Header="XAML Inline">
            <Grid ColumnDefinitions="*, Auto">
                <ScrollViewer
                    Name="container1"
                    Grid.Column="0"
                    VerticalAlignment="Stretch">
                    <StackPanel>
                        <StackPanel.Styles>
                            <Style Selector="TextBlock">
                                <Setter Property="HorizontalAlignment" Value="Center" />
                                <Setter Property="VerticalAlignment" Value="Center" />
                            </Style>
                        </StackPanel.Styles>
                        <Border
                            u:Anchor.AnchorId="a1"
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiRed2}">
                            <TextBlock Text="Border 1" />
                        </Border>
                        <Border
                            u:Anchor.AnchorId="a2"
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiPink1}">
                            <TextBlock Text="Border 2" />
                        </Border>
                        <Border
                            u:Anchor.AnchorId="a3"
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiPurple1}">
                            <TextBlock Text="Border 3" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiViolet1}">
                            <TextBlock u:Anchor.AnchorId="a4" Text="Border 4" />
                        </Border>
                        <Border
                            u:Anchor.AnchorId="a5"
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiIndigo1}">
                            <TextBlock Text="Border 5" />
                        </Border>
                        <Border
                            u:Anchor.AnchorId="a6"
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiBlue1}">
                            <TextBlock Text="Border 6" />
                        </Border>
                        <Border
                            u:Anchor.AnchorId="a7"
                            Height="300"
                            HorizontalAlignment="Stretch"
                            Background="{DynamicResource SemiLightBlue1}">
                            <TextBlock Text="Border 7" />
                        </Border>
                    </StackPanel>
                </ScrollViewer>
                <u:Anchor
                    Grid.Column="1"
                    Width="200"
                    Margin="24"
                    TargetContainer="{Binding ElementName=container1}">
                    <u:AnchorItem Header="Rectangle 1" AnchorId="a1" >
                        <u:AnchorItem Header="Rectangle 2" AnchorId="a2" />
                        <u:AnchorItem Header="Rectangle 3" AnchorId="a3" />
                    </u:AnchorItem>
                    <u:AnchorItem Header="Rectangle 4" AnchorId="a4" />
                    <u:AnchorItem Header="Rectangle 5" AnchorId="a5" >
                        <u:AnchorItem Header="Rectangle 6" AnchorId="a6" />
                        <u:AnchorItem Header="Rectangle 7" AnchorId="a7" />
                    </u:AnchorItem>


                </u:Anchor>
            </Grid>
        </TabItem>
        <TabItem Header="MVVM">
            <Grid ColumnDefinitions="*, Auto">
                <ScrollViewer
                    Name="container2"
                    Grid.Column="0"
                    VerticalAlignment="Stretch">
                    <StackPanel>
                        <StackPanel.Styles>
                            <Style Selector="TextBlock">
                                <Setter Property="HorizontalAlignment" Value="Center" />
                                <Setter Property="VerticalAlignment" Value="Center" />
                            </Style>
                        </StackPanel.Styles>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor1"
                            Background="{DynamicResource SemiRed2}">
                            <TextBlock Text="Border 1" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor2"
                            Background="{DynamicResource SemiPink1}">
                            <TextBlock Text="Border 2" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor3"
                            Background="{DynamicResource SemiPurple1}">
                            <TextBlock Text="Border 3" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor3-1"
                            Background="{DynamicResource SemiPurple1}">
                            <TextBlock Text="Border 3-1" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor3-2"
                            Background="{DynamicResource SemiPurple1}">
                            <TextBlock Text="Border 3-2" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor3-3"
                            Background="{DynamicResource SemiPurple1}">
                            <TextBlock Text="Border 3-3" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor4"
                            Background="{DynamicResource SemiViolet1}">
                            <TextBlock Text="Border 4" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor5"
                            Background="{DynamicResource SemiIndigo1}">
                            <TextBlock Text="Border 5" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor6"
                            Background="{DynamicResource SemiBlue1}">
                            <TextBlock Text="Border 6" />
                        </Border>
                        <Border
                            Height="300"
                            HorizontalAlignment="Stretch"
                            u:Anchor.AnchorId="anchor7"
                            Background="{DynamicResource SemiLightBlue1}">
                            <TextBlock Text="Border 7" />
                        </Border>
                    </StackPanel>
                </ScrollViewer>
                <u:Anchor
                    Grid.Column="1"
                    Width="200"
                    Margin="24"
                    ItemsSource="{Binding AnchorItems}"
                    TargetContainer="{Binding #container2}">
                    <u:Anchor.Styles>
                        <Style x:DataType="viewModels:AnchorItemViewModel" Selector="u|AnchorItem">
                            <Setter Property="AnchorId" Value="{Binding AnchorId}" />
                        </Style>
                    </u:Anchor.Styles>
                    <u:Anchor.ItemTemplate>
                        <TreeDataTemplate ItemsSource="{Binding Children}">
                            <TextBlock Text="{Binding Header}"/>
                        </TreeDataTemplate>
                    </u:Anchor.ItemTemplate>
                </u:Anchor>
            </Grid>
        </TabItem>
    </TabControl>
</UserControl>