canvas not updated real-time by background thread

In .NET4.0 WPF, I want to display a drawingPath on a canvas using a background thread. The following ConsumerJob is correctly running in the background and polling a queue of points to draw. I use a Dispatcher to modify the canvas on the main thread and it gets correctly rendered. However, I would expect this code to display each segment one at a time as and when each children.add gets invoked(like an animation). What happens is that the whole display gets rendered at once and not one segment at a time.开发者_如何学运维 How should I modify the code to render the display as the children get added one at a time?

public void ConsumerJob()
    {

        while (true)
        {
            PointsD pt = (PointsD)queue.Consume();
            displayQueue.Enqueue(pt);

            pt = Scale(pt);

            this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
                (ThreadStart)delegate()
                {
                    Path drawingPath = new Path();
                    StreamGeometry streamingGeometry = new StreamGeometry();
                    drawingPath.Stroke = Brushes.Black;
                    drawingPath.StrokeThickness = 0.5;

                    using (StreamGeometryContext ctx = streamingGeometry.Open())
                    {
                            ctx.BeginFigure(new Point(pt.x0, pt.y0), false, false);
                            ctx.LineTo(new Point(pt.x1, pt.y1), true, false);
                    }

                    streamingGeometry.Freeze();
                    drawingPath.Data = streamingGeometry;

                    this.Children.Add(drawingPath);

                }
                );

        }

Dispatcher.BeginInvoke is asynchronous, have you tried its synchronous counterpart Invoke?

That should at least enforce that all queued delegates are executed in the right order, not sure about the timing though.

You might also want to try a higher DispatcherPriority in addition to that.