Hi,

The only way I can think of doing that currently is to create a custom DiagramLink class that adds a new dependency property for binding and overrides UpdateVisuals to update the property. UpdateVisuals is called every time the link points change their position. For binding in the other direction, you could update ControlPoints from the OnChanged callback you register with the custom dependency property.

I hope that helps,
Stoyan

Here's a sample class:

class BoundLink : DiagramLink
{
	public BoundLink(Diagram diagram, DiagramNode origin, DiagramNode destination)
		: base(diagram,origin, destination)
	{
		updating = true;
		Points = new List<Point>(ControlPoints);
		updating = false;
	}

	public List<Point> Points
	{
		get { return (List<Point>)GetValue(PointsProperty); }
		set { SetValue(PointsProperty, value); }
	}

	static public DependencyProperty PointsProperty = DependencyProperty.Register(
		"Points", typeof(List<Point>), typeof(BoundLink), new PropertyMetadata(null, OnPointsChanged));

	private static void OnPointsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
	{
		var link = (BoundLink)d;
		link.OnPointsChanged();
	}

	private void OnPointsChanged()
	{
		if (updating)
			return;

		updating = true;
		SegmentCount = Points.Count - 1;
		ControlPoints.Clear();
		ControlPoints.AddRange(Points);
		UpdateFromPoints();
		updating = false;
	}

	protected override void UpdateVisuals()
	{
		base.UpdateVisuals();

		if (updating)
			return;

		updating = true;
		Points = new List<Point>(ControlPoints);
		updating = false;
	}

	bool updating;
} 

Above binding will work when you assign a new list to Points, but will not detect adding new points to the list. If you need that, you must use a list class that implements INotifyCollectionChanged, and handle its CollectionChanged event to refresh the link points. E.g. a Silverlight list class that already implements this interface is ObservableCollection.

I hope that helps,
Stoyan