Scales a rectangle by 200% from a center of (25,25)

   
  
<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="250" Height="250">
          <Rectangle Height="50" Width="50" Fill="#CCCCCCFF"
            Canvas.Left="100" Canvas.Top="100" Stroke="Blue" StrokeThickness="2">
            <Rectangle.RenderTransform>
              <ScaleTransform CenterX="25" CenterY="25" ScaleX="2" ScaleY="2" />
            </Rectangle.RenderTransform>
          </Rectangle>
          <Rectangle Style="{StaticResource MarkerRectangleStyle}" />        
        </Canvas>

</Window>