LinearGradientPath and GradientStopCollection
<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'> <Grid x:Name="LayoutRoot" Background="White"> <Rectangle Width="200" Height="200"> <Rectangle.Fill> <LinearGradientBrush> <GradientStopCollection> <GradientStop Color="Yellow" Offset="0.5" /> <GradientStop Color="Red" Offset="1.0" /> </GradientStopCollection> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> </Grid> </UserControl>