Did You Know That… You can get sharp lines within a linear gradient?

This tip is thanks to Adam Nathan and his excellent book Silverlight 1.0 Unleashed

You can achieve the startling effect of introducing sharp lines within a linear gradient by adding two GradientStops at the same offset, using different, and reinforcing colors.  In the following example, I show two polygons. The first uses a standard gradient brush, but in the second I introduce a new color (DarkBlue) which I place at the same GradientStop as Green and at the same GradientStop as Blue. The effect is quite unmistakable, as shown in the image.

<Canvas xmlns="http://schemas.microsoft.com/client/2007" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Polygon x:Name="PolyWithGradientBrush"
         Points= "50,70, 100,70, 150,120, 150,170, 100,220, 
         50,220, 0,170, 0,120, 50,70"
         StrokeThickness="2"
         Stroke="Black" >
  <Polygon.Fill>
         <LinearGradientBrush>
            <GradientStop Color="Red"
                          Offset="0.0" />
            <GradientStop Color="Orange"
                          Offset="0.3" />
            <GradientStop Color="Green"
                          Offset="0.5" />
            <GradientStop Color="Blue"
                          Offset="0.7" />
            <GradientStop Color="Violet"
                          Offset="1.0" />
         </LinearGradientBrush>
      </Polygon.Fill>
</Polygon>

   <Polygon x:Name="PolyWithGradientBrushAndSharpLines"
            Points="250,70, 300,70, 350,120, 350,170, 300,220, 
         250,220, 200,170, 200,120, 250,70"
            StrokeThickness="2"
            Stroke="Black">
      <Polygon.Fill>
         <LinearGradientBrush>
            <GradientStop Color="Red"
                          Offset="0.0" />
            <GradientStop Color="Orange"
                          Offset="0.3" />
            <GradientStop Color="Green"
                          Offset="0.5" />
            <GradientStop Color="DarkBlue"
                          Offset="0.5" />
            <GradientStop Color="DarkBlue"
                          Offset="0.7" />
            <GradientStop Color="Blue"
                          Offset="0.7" />
            <GradientStop Color="Violet"
                          Offset="1.0" />
         </LinearGradientBrush>
      </Polygon.Fill>
   </Polygon>
</Canvas>