Thank you for your question.
You cannot get a collection of Points from a RadDiagramShape
out of the box. However, this can be achieved by using some custom logic. In order to do it you will need to get the flattened PathGeometry of the Shape with the GetFlattenedPathGeometry() method. Then you should get every Point of every PathSegment in the PathGeometry.
In the next few lines I will try to explain how exactly you can get those points. Let's begin with that every PathGeometry has a collection of PathFigures and every PathFigure in this collection has a PathSegments collection. When the collection is flattened the PathSegments collection contains only PolylineSegments and every one of those segments has a collection of Points which you may use to achieve your requirement. Here is an example in code:
PathGeometry pathGeometry = shape.Geometry.GetFlattenedPathGeometry();
var pointCollection =
var polySegment = segment
Point newPoint =
X = point.X +
Y = point.Y +
I also attached a sample project with the described approach.