MARKUS

                instanceGroup.Children.Add(SingleAllow(this.StartPoint, this.EndPoint, this.LineSize));

                instanceGroup.Children.Add(SingleAllow(this.MiddlePoint, this.EndPoint, this.LineSize));

        public static PathGeometry SingleAllow(Point p2, Point p1, double lineSize)

        {

            double theta = Math.Atan2((p2.Y - p1.Y), (p2.X - p1.X)) * 180 / Math.PI;

            PathGeometry pathGeometry = new PathGeometry();

            PathFigure pathFigure = new PathFigure();

            pathFigure.StartPoint = p1;

            //lineSize = 2;

            Point lpoint = new Point(p1.X + lineSize * 3, p1.Y + lineSize * 6);

            Point rpoint = new Point(p1.X - lineSize * 3, p1.Y + lineSize * 6);

            LineSegment seg1 = new LineSegment();

            seg1.Point = lpoint;

            pathFigure.Segments.Add(seg1);

            LineSegment seg2 = new LineSegment();

            seg2.Point = rpoint;

            pathFigure.Segments.Add(seg2);

            LineSegment seg3 = new LineSegment();

            seg3.Point = p1;

            pathFigure.Segments.Add(seg3);

            pathFigure.IsClosed = true;

            pathFigure.IsFilled = true;

            pathGeometry.Figures.Add(pathFigure);

            pathGeometry.FillRule = FillRule.Nonzero;

            RotateTransform transform = new RotateTransform();

            transform.Angle = theta - 90;

            transform.CenterX = p1.X;

            transform.CenterY = p1.Y;

            pathGeometry.Transform = transform;

            return pathGeometry;

        }