Use RadialGradientBrush to fill Ellipse
<UserControl x:Class='SilverlightApplication3.MainPage' xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml' xmlns:d='http://schemas.microsoft.com/expression/blend/2008' xmlns:mc='http://schemas.openxmlformats.org/markup-compatibility/2006' mc:Ignorable='d' d:DesignWidth='640' d:DesignHeight='480'> <Canvas xmlns="http://schemas.microsoft.com/client/2007"> <Ellipse Width="450" Height="450"> <Ellipse.Fill> <RadialGradientBrush> <RadialGradientBrush.GradientStops> <GradientStop Color="White" Offset="0"/> <GradientStop Color="Black" Offset="1"/> </RadialGradientBrush.GradientStops> </RadialGradientBrush> </Ellipse.Fill> </Ellipse> </Canvas> </UserControl>