NCompositeShape shape = new NCompositeShape();
NRectangleShape rectx = new NRectangleShape(new NRectangleF(150, 150, 50, 50));

NShape rect2 = factory.CreateShape(BasicShapes.Rectangle);
rect2.Bounds = new NRectangleF(250, 200, 75, 75);
rect2.CreateShapeElements(ShapeElementsMask.Ports);
rect2.Style.FillStyle = new NColorFillStyle(Color.Empty);

NPolygonPath cup = new NPolygonPath(new NPointF[]{ new NPointF(45, 268),
  new NPointF(63, 331),
  new NPointF(121, 331),
  new NPointF(140, 268)});

//document1.ActiveLayer.AddChild(rect2);
shape.Primitives.AddChild(cup);
shape.Primitives.AddChild(rectx); // an exception is raised here
shape.Primitives.AddChild(rect2);// an exception is raised here