This rectangle is painted with a vertical gradient

   
  
<Window x:Class="Workspace.DockExample"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Workspace" Width="640" Height="480">
    <Canvas Width="200" Height="100">
      <Rectangle Width="200" Height="100">
        <Rectangle.Fill>
          <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
            <LinearGradientBrush.GradientStops>
              <GradientStop Color="Yellow" Offset="0" />
              <GradientStop Color="Red" Offset="0.25" />
              <GradientStop Color="Blue" Offset="0.75" />
              <GradientStop Color="LimeGreen" Offset="1" />
            </LinearGradientBrush.GradientStops>
          </LinearGradientBrush>
        </Rectangle.Fill>
      </Rectangle>
      <Line X1="100" Y1="1" X2="100" Y2="99" />
      <Path>
        <Path.Data>
          <GeometryGroup>
            <EllipseGeometry Center="100,0" RadiusX="4" RadiusY="4" />
            <EllipseGeometry Center="100,25" RadiusX="4" RadiusY="4" />
            <EllipseGeometry Center="100,75" RadiusX="4" RadiusY="4" />
            <EllipseGeometry Center="100,100" RadiusX="4" RadiusY="4" />
          </GeometryGroup>
        </Path.Data>
      </Path>
    </Canvas>

</Window>