I am working on extending the Microsoft resize Adorner
example and need to be able to reposition the element after say the bottom left drag handle has been drag
You can transform coordinates of the UIElement
to its parent. In your case it's a form. Here is an example of a method that returns coordinates of a visual:
private Point GetPosition(Visual element) {
var positionTransform = element.TransformToAncestor(MyForm);
var areaPosition = positionTransform.Transform(new Point(0, 0));
return areaPosition;
}