protected override void OnRender(DrawingContext dc)
{
base.OnRender(dc);
foreach (AlignPart it1 in w_parts.Items)
{
var cp1 = (ContentPresenter)w_parts.ItemContainerGenerator.ContainerFromItem(it1);
var bi1 = VisualTreeHelper.GetChild(cp1, 0) as ToggleButton;
var r1 = new Rect(bi1.DesiredSize);
var pt1 = bi1.TransformToAncestor(this).Transform(r1.BottomCenter());
foreach (var it2 in it1.AlignedParts)
{
var cp2 = (ContentPresenter)w_alignwith.ItemContainerGenerator.ContainerFromItem(it2);
var bi2 = VisualTreeHelper.GetChild(cp2, 0) as Button;
var r2 = new Rect(bi2.DesiredSize);
var pt2 = bi2.TransformToAncestor(this).Transform(r2.TopCenter());
dc.DrawLine(new Pen(Brushes.Black, 2), pt1, pt2);
}
}
}