Avalonia/samples/ControlCatalog/DecoratedWindow.xaml

<Window xmlns="https://github.com/avaloniaui" MinWidth="500" MinHeight="300"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Class="ControlCatalog.DecoratedWindow"
        Title="Avalonia Control Gallery"
        SystemDecorations="None" Name="Window">
        <NativeMenu.Menu>
    <NativeMenu>
      <NativeMenuItem Header="Decorated">
        <NativeMenu>
          <NativeMenuItem Header="Open"/>
          <NativeMenuItem Header="Recent">
            <NativeMenuItem.Menu>
              <NativeMenu/>
            </NativeMenuItem.Menu>
          </NativeMenuItem>
          <NativeMenuItem Header="Quit Avalonia" Gesture="CMD+Q"/>
        </NativeMenu>
      </NativeMenuItem>
      <NativeMenuItem Header="Edit">
        <NativeMenu>
          <NativeMenuItem Header="Copy"/>
          <NativeMenuItem Header="Paste"/>
        </NativeMenu>
      </NativeMenuItem>
    </NativeMenu>
  </NativeMenu.Menu>
    <Grid RowDefinitions="5,*,5" ColumnDefinitions="5,*,5">
        <DockPanel  Grid.Column="1"  Grid.Row="1" >
            <Grid Name="TitleBar" Background="LightBlue" DockPanel.Dock="Top" ColumnDefinitions="Auto,*,Auto">
                <TextBlock VerticalAlignment="Center" Margin="5,0,0,0">Title</TextBlock>
                <StackPanel Grid.Column="2" Orientation="Horizontal">
                    <StackPanel.Styles>
                        <Style Selector="Button">
                            <Setter Property="Margin" Value="2"/>
                        </Style>
                    </StackPanel.Styles>
                    <Button Name="MinimizeButton">_</Button>
                    <Button Name="MaximizeButton">[ ]</Button>
                    <Button Name="CloseButton">X</Button>
                </StackPanel>
            </Grid>
            <Border Background="White" Margin="5">
                <StackPanel>
                    <TextBlock>Hello world!</TextBlock>

                    <ComboBox SelectedItem="{Binding ElementName=Window, Path=SystemDecorations}">
                      <ComboBox.Items>
                        <SystemDecorations>None</SystemDecorations>
                        <SystemDecorations>BorderOnly</SystemDecorations>
                        <SystemDecorations>Full</SystemDecorations>
                      </ComboBox.Items>
                    </ComboBox>
                    <CheckBox IsChecked="{Binding ElementName=Window, Path=CanResize}">CanResize</CheckBox>
                </StackPanel>
            </Border>
        </DockPanel>
        <Border Name="TopLeft" Background="Red"/>
        <Border Name="TopRight" Background="Red" Grid.Column="2" />
        <Border Name="BottomLeft" Background="Red" Grid.Row="2" />
        <Border Name="BottomRight" Background="Red"  Grid.Row="2" Grid.Column="2"/>
        <Border Name="Top" Background="Blue" Grid.Column="1" />
        <Border Name="Right" Background="Blue" Grid.Row="1"  Grid.Column="2" />
        <Border Name="Bottom" Background="Blue" Grid.Row="2" Grid.Column="1"  />
        <Border Name="Left" Background="Blue"  Grid.Row="1" />
    </Grid>
</Window>