You can check our Diagram Custom Services SDK Sample
which demonstrates how you can customize Diagram Dragging Service to restrict dragging of shapes in some area. I used this approach and modified it to restrict the dragged shape in the Bounds of the shape's parent container. Could you please check it out in the attached project and let us know if this is what you needed ?
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.