Avalonia/samples/ControlCatalog/Pages/BorderPage.paml

<UserControl xmlns="https://github.com/perspex">
  <StackPanel Orientation="Vertical" Gap="4">
    <TextBlock Classes="h1">Border</TextBlock>
    <TextBlock Classes="h2">A control which decorates a child with a border and background</TextBlock>

    <StackPanel Orientation="Vertical"
                Margin="0,16,0,0"
                HorizontalAlignment="Center"
                Gap="16">
      <Border BorderBrush="#f44336" BorderThickness="2" Padding="16">
        <TextBlock>Border</TextBlock>
      </Border>
      <Border Background="#f44336" BorderBrush="#4285f4" BorderThickness="4" Padding="16">
        <TextBlock>Border and Background</TextBlock>
      </Border>
      <Border BorderBrush="#4285f4" 
              BorderThickness="4" 
              CornerRadius="8"
              Padding="16">
        <TextBlock>Rounded Corners</TextBlock>
      </Border>
      <Border Background="#f44336" 
              CornerRadius="8"
              Padding="16">
        <TextBlock>Rounded Corners</TextBlock>
      </Border>
    </StackPanel>    
  </StackPanel>
</UserControl>