Polyline polyline = x as Polyline;
                    if (polyline != null)
                        polyline.Points[ix] = DoSomething(x);

                    Polygon polygon = x as Polygon;
                    if (polygon != null)
                        polygon.Points[ix] = DoSomething(x);

                    MyShape line = x as MyShape;
                    if (line != null)
                        line.Points[ix] = DoSomething(x);