Remember this syntax from the early days of Avalon/WPF/XAML?

<Rectangle Width="300" Height="200"
    Fill="HorizontalGradient Blue White" >
</Rectangle>

Very simple — easy to create Gradient Brush. But, it was removed from Avalon/WPF in part due to it’s challenge for tools (parsing, etc.).

Mike posts a simple MarkupExtension that although it doesn’t mimic the old syntax identically, the spirit is there.

<Rectangle Width="300" Height="200"
  Fill="{local:RadialGradientBrush red, blue}" />