how to "find a point" about geojson.net HOT 3 CLOSED

            using GeoJSON.Net;
            using GeoJSON.Net.Feature;
            using NetTopologySuite.Geometries;

            string topology_string = File.ReadAllText("ne_10m_time_zones.geojson"));

            // create NetTopology JSON reader
            var reader = new NetTopologySuite.IO.GeoJsonReader();

            // pass geoJson's FeatureCollection to read all the features
            var featureCollection = reader.Read<GeoJSON.Net.Feature.FeatureCollection>(topology_string);

            // if feature collection is null then return 
            if (featureCollection == null)
            {
                return;
            }

            // loop through all the parsed featurd   
            for (int featureIndex = 0;
                 featureIndex < featureCollection.Features.Count;
                 featureIndex++)
            {
                // get json feature
                var jsonFeature = featureCollection.Features[featureIndex];
                Geometry geom = null;

                // get geometry type to create appropriate geometry
                switch (jsonFeature.Geometry.Type)
                {
                    case GeoJSONObjectType.Point:
                        break;
                    case GeoJSONObjectType.MultiPoint:
                        break;
                    case GeoJSONObjectType.LineString:
                        break;
                    case GeoJSONObjectType.MultiLineString:
                        break;
                    case GeoJSONObjectType.Polygon:
                        {
                            var polygon = jsonFeature.Geometry as GeoJSON.Net.Geometry.Polygon;

                            List<Coordinate> coordinates = new List<Coordinate>();
                            foreach (var ring in polygon.Coordinates)
                            {
                                if (ring.IsLinearRing())
                                {
                                    foreach (var coordinate in ring.Coordinates)
                                    {
                                        coordinates.Add(new Coordinate(coordinate.Latitude, coordinate.Longitude));
                                    }
                                }
                            }
                            //Add first Point again to be sure to have a closed Polygon
                            //may you have to remove this line:
                            coordinates.Add(new Coordinate(coordinates[0].X, coordinates[0].Y));

                            var poly = new Polygon(new LinearRing(coordinates.ToArray()));
                            if (poly.Contains(new Point(x, y))
                                FounTimeZoneForPoint();
                        }
                        break;
                    case GeoJSONObjectType.MultiPolygon:
                        break;
                    case GeoJSONObjectType.GeometryCollection:
                        break;
                    case GeoJSONObjectType.Feature:
                        break;
                    case GeoJSONObjectType.FeatureCollection:
                        break;
                    default:
                        throw new ArgumentOutOfRangeException();
                }
            }