The points of a Polygon are retrieved and set by value; therefore new points are always copied in to the Polygon, not added directly. Polygon methods without a ring index parameter work for both single part and multipart polygons; if called on a multipart Polygon, methods without a ring index work against the first ring in the Polygon.

Note that the CoordinateSystem property of any new points added, inserted or set into existing an existing Polygon or Polyline will be discarded, and the coordinates (X and Y properties) of the point assumed to be in the same CoordinateSystem as the Polygon or Polyline to which they are added.