Avalonia/samples/BindingTest/MainWindow.paml

<Window xmlns="https://github.com/perspex">
  <StackPanel Margin="18" Gap="4">
    <TextBlock Text="{Binding SimpleBinding}"/>
    <TextBox Watermark="Two Way" Text="{Binding SimpleBinding}"/>
    <TextBox Watermark="One Way" Text="{Binding SimpleBinding, Mode=OneWay}"/>
    <TextBox Watermark="One Time" Text="{Binding SimpleBinding, Mode=OneTime}"/>
    <TextBox Watermark="One Way To Source" Text="{Binding SimpleBinding, Mode=OneWayToSource}"/>
  </StackPanel>
</Window>