Avalonia/samples/ControlCatalog/Pages/RadioButtonPage.xaml

<UserControl xmlns="https://github.com/avaloniaui">
  <StackPanel Orientation="Vertical" Gap="4">
    <TextBlock Classes="h1">RadioButton</TextBlock>
    <TextBlock Classes="h2">Allows the selection of a single option of many</TextBlock>

    <StackPanel Orientation="Vertical"
                Margin="0,16,0,0"
                HorizontalAlignment="Center"
                Gap="16">
      <RadioButton IsChecked="True">Option 1</RadioButton>
      <RadioButton>Option 2</RadioButton>
      <RadioButton IsEnabled="False">Disabled</RadioButton>
    </StackPanel>    
  </StackPanel>
</UserControl>