WPF absolute positioning in InkCanvas

I am trying to position a rectangle in a InkCanvas

. I am using the following method. Unfortunately, when I add a rectangle it displays in (0,0)

. Although, when I ask to see if the property has left 0

, I get non-null values. Does anyone know why this might be?

Greetings,

Nilu

InkCanvas _parent = new InkCanvas();
private void AddDisplayRect(Color annoColour, Rect bounds)
    {
        Rectangle displayRect = new Rectangle();
        Canvas.SetTop(displayRect, bounds.Y);
        Canvas.SetLeft(displayRect, bounds.X);

        // check to see if the property is set
        Trace.WriteLine(Canvas.GetLeft(displayRect));
        displayRect.Width = bounds.Width;
        displayRect.Height = bounds.Height;
        displayRect.Stroke = new SolidColorBrush(annoColour);
        displayRect.StrokeThickness = 1;

        _parent.Children.Add(displayRect);            
    }