ToGoogleMapsPolygon

gistfile1.cs

        public static List<List<Coordinate>> ToGoogleMapsPolygon(this DbGeography dbGeo)
        {
            // contains all geo data for one postal code / admin area code
            // conversion to SqlGeography because DbGeography does not offer properties to determine rings within geometries. we need those ring information to display areas with holes
            var sqlGeo = (SqlGeography) dbGeo.ProviderValue;

            var numberOfGeometries = sqlGeo.STNumGeometries();
            var result = new List<List<Coordinate>>((int) numberOfGeometries);

            // at first we iterate over all geometries within our sqlGeo object to get all polygones in case we have to deal with a multipolygone
            for (int k = 1; k <= numberOfGeometries; k++)
            {
                var sqlGeography = sqlGeo.STGeometryN(k);

                // if we one of our geometries has rings defined on it, we know that this area contain holes
                if (!sqlGeography.NumRings().IsNull)
                {
                    var numberOfRings = sqlGeography.NumRings();

                    // we now add one path for each ring
                    for (int i = 1; i <= numberOfRings; i++)
                    {
                        var ringGeography = sqlGeography.RingN(i);

                        var numberOfCoordinatesInRing = ringGeography.STNumPoints();

                        var path = new List<Coordinate>((int) numberOfCoordinatesInRing);
                        // a path is a list of coordinates; a coordinate consists of a Latitude and Longitude value
                        for (int n = 1; n <= numberOfCoordinatesInRing; n++)
                        {
                            path.Add(new Coordinate
                                {
                                    Latitude = (double) ringGeography.STPointN(n).Lat,
                                    Longitude = (double) ringGeography.STPointN(n).Long,
                                });
                        }

                        result.Add(path);
                    }
                }
            }
            return result;
        }