Some problems with MultiPolygon and MultiLineString GeoJson

[mfandre]

I create this method, that connects to some Esri MapServer and gets all geometries and creates a GEOJSON:

public async Task<FeatureCollection<IGeoJsonGeometry>> QueryAllFromMapserviceLayer(string server, string service, string layer)
        {
            //http://app.anp.gov.br/arcgis/rest/services/ANP_Public_Confidential/MapServer/0/query

            var gateway = new PortalGateway(server); //"http://app.anp.gov.br/arcgis/"

            var query = new Query((service + "/MapServer/" + layer).AsEndpoint());
            query.ReturnGeometry = true;

            FeatureCollection<IGeoJsonGeometry> featureCollectionGeoJson = null;
            int? Wkid = 0;
            if (await this.GetLayerType(server, service, layer) == "esriGeometryPolyline")
            {
                var result = await gateway.BatchQuery<Anywhere.ArcGIS.Common.Polyline>(query);
                Wkid = result.SpatialReference.Wkid;
                //var count = result.Features.Count();
                featureCollectionGeoJson = FeatureCollectionExtensions.ToFeatureCollection<Anywhere.ArcGIS.Common.Polyline>(result.Features.ToList());
                
            }

            if (await this.GetLayerType(server, service, layer) == "esriGeometryPoint")
            {
                var result = await gateway.BatchQuery<Anywhere.ArcGIS.Common.Point>(query);
                Wkid = result.SpatialReference.Wkid;
                //var count = result.Features.Count();
                featureCollectionGeoJson = FeatureCollectionExtensions.ToFeatureCollection<Anywhere.ArcGIS.Common.Point>(result.Features.ToList());
            }

            if (await this.GetLayerType(server, service, layer) == "esriGeometryPolygon")
            {
                var result = await gateway.BatchQuery<Anywhere.ArcGIS.Common.Polygon>(query);
                Wkid = result.SpatialReference.Wkid;
                //var count = result.Features.Count();
                featureCollectionGeoJson = FeatureCollectionExtensions.ToFeatureCollection<Anywhere.ArcGIS.Common.Polygon>(result.Features.ToList());

                //por algum motivo ao gerar o geojson algumas features estão vindo zuadas... essa trecho remove as features zuadas do poligono
                foreach(var temp in featureCollectionGeoJson.Features)
                {
                    PointCollectionList fixedCoords = new PointCollectionList();
                    foreach (var coord in ((GeoJsonPolygon)temp.Geometry).Coordinates)
                    {
                        if (coord.Count > 3)
                            fixedCoords.Add(coord);
                    }

                    ((GeoJsonPolygon)temp.Geometry).Coordinates = fixedCoords;
                }
            }

            foreach (var geom in featureCollectionGeoJson.Features)
            {
                geom.Id = Guid.NewGuid().ToString();
            }
            featureCollectionGeoJson.Type = "FeatureCollection";
            featureCollectionGeoJson.CoordinateReferenceSystem = new Crs { Type = "name", Properties = new CrsProperties { Name = Wkid.HasValue ? "EPSG:" + Wkid : null} };

            return featureCollectionGeoJson;
        }

I used the following parameters:

• server=http://app.anp.gov.br/arcgis/
• service=ANP_Public_Confidential
• layer=2

The problem is that layer has some multilines then the geojson generated is invalid... Not represent the same features that original.

I think the problem is in this line: featureCollectionGeoJson = FeatureCollectionExtensions.ToFeatureCollection<Anywhere.ArcGIS.Common.Polyline>(result.Features.ToList());

I think the lib need to create a new model for these kinds of geometries.

[davetimmins]

I've never really used the GeoJSON conversion in anger so there are likely some issues, especially with something like you're trying to convert. Since ArcGIS Server can output GeoJSON natively now I haven't looked at updating it either. If you're stuck on an old version you'll have to look at converting it yourself or using another lib to do it.