MongoDB .NET Driver not deserializing for collection
I'm having an issue with deserializing a collection from MongoDB. It seems fine for a single object but fails for a collection of objects. The collection is a GeoJSON object in Mongo with coordinates. That seems to be the problem. Perhaps I'm not representing that right in my C# class. Though it seems to work fine for a single object.
I created a generic collection repo according to this post: Generic Mongo Repository pattern implemented in .NET Core
Given my class:
using System.Collections.Generic;
using MongoDB.Driver.GeoJsonObjectModel;
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;
namespace VisualStatsPoCAPI.Repositories.Models.Mongo
{
[BsonCollection("garda_subdistrict_boundaries")]
public class GardaSubdistrictBoundaryMongo : Document
{
[BsonElement("type")]
public string Type { get; set; }
[BsonElement("properties")]
public Properties Properties { get; set; }
[BsonElement("geometry")]
public Geometry Geometry { get; set; }
}
public class Properties
{
public string REGION { get; set; }
public string REG_CODE { get; set; }
public string DIVISION { get; set; }
public string DIV_CODE { get; set; }
public string DISTRICT { get; set; }
public string DIST_CODE { get; set; }
public string SUB_DIST { get; set; }
public string SUB_IRISH { get; set; }
public string SUB_CODE { get; set; }
public string COUNTY_1 { get; set; }
public string COUNTY_2 { get; set; }
public string GEOGID { get; set; }
public int Male2011 { get; set; }
public int Female2011 { get; set; }
public int Total2011 { get; set; }
public int PPOcc2011 { get; set; }
public int Unocc2011 { get; set; }
public int Vacant2011 { get; set; }
public int HS2011 { get; set; }
public double PCVac2011 { get; set; }
public string CREATEDBY { get; set; }
}
public class Geometry
{
[BsonElement("type")]
public string Type { get; set; }
[BsonElement("coordinates")]
public IEnumerable<IEnumerable<GeoJson2DCoordinates>> Coordinates { get; set; }
}
}
and the MongoDB collection:
and small snippet of the doument itself (which I converted from a Shapefile according to Importing a Shapefile into MongoDB using GeoJSON):
[
{ "type": "Feature",
"properties": {
"REGION": "Southern Region",
"REG_CODE": "03",
"DIVISION": "Cork West",
"DIV_CODE": "0319",
"DISTRICT": "Bandon",
"DIST_CODE": "4300A",
"SUB_DIST": "Kinsale",
"SUB_IRISH": "Cionn tS�ile",
"SUB_CODE": "4305B",
"COUNTY_1": "Cork",
"COUNTY_2": null,
"GEOGID": "M4305B",
"Male2011": 5765,
"Female2011": 5963,
"Total2011": 11728,
"PPOcc2011": 4054,
"Unocc2011": 1177,
"Vacant2011": 1013,
"HS2011": 5231,
"PCVac2011": 19.4,
"CREATEDBY": "Paul Creaner"
},
"geometry": {
"type": "Polygon",
"coordinates": [
[
[-8.665517347801826, 51.701921804534543 ],
[-8.665512199746647, 51.702050730841847 ]
]
]
}
}
]
I get an error:
System.FormatException: An error occurred while deserializing the Geometry property of class VisualStatsPoCAPI.Repositories.Models.Mongo.GardaSubdistrictBoundaryMongo: An error occurred while deserializing the Coordinates property of class VisualStatsPoCAPI.Repositories.Models.Mongo.Geometry: Cannot deserialize a 'Double' from BsonType 'Array'.
The SDK call I'm using for a single object is:
public virtual TDocument FindOne(Expression<Func<TDocument, bool>> filterExpression)
{
return _collection.Find(filterExpression).FirstOrDefault();
}
and for a collection, either:
public virtual IEnumerable<TProjected> FilterBy<TProjected>(
Expression<Func<TDocument, bool>> filterExpression,
Expression<Func<TDocument, TProjected>> projectionExpression)
{
return _collection.Find(filterExpression).Project(projectionExpression).ToEnumerable();
}
or
public virtual Task<IEnumerable<TDocument>> FindAll()
{
FilterDefinition<TDocument> filter = FilterDefinition<TDocument>.Empty;
return Task.Run(() => _collection.Find(filter).ToList().AsEnumerable());
}
It has something to do with how I'm representing the geometry but I'm unsure. I'm a bit confused. Can anyone help?
Update (25 Mar 2020): It was suggested that I use GeoJsonPolygon. I tried using that like below:
public GeoJsonPolygon<GeoJson2DCoordinates> Geometry { get; set; }
Again, that works fine for a single document. When I try using that for an entire collection, I get:
System.FormatException: An error occurred while deserializing the Geometry property of class VisualStatsPoCAPI.Repositories.Models.Mongo.GardaSubdistrictBoundaryMongo: Invalid GeoJson type: 'MultiPolygon'. Expected: 'Polygon'.
When I switch to using a GeoJsonMultiPolygon (as the compiler suggests), I get:
System.FormatException: An error occurred while deserializing the Geometry property of class VisualStatsPoCAPI.Repositories.Models.Mongo.GardaSubdistrictBoundaryMongo: Invalid GeoJson type: 'Polygon'. Expected: 'MultiPolygon'.
It's unclear from the screenshot and model provided but became clear when you pasted the errors you're getting.
It looks like your collection contains both Polygons:
{ geometry: { 'type' : 'Polygon', 'coordinates' : [[[100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 0.0]]] } }
and MultiPolygons:
{ geometry: { 'type' : 'MultiPolygon', 'coordinates' : [[[[102.0, 2.0], [103.0, 2.0], [103.0, 3.0], [102.0, 3.0], [102.0, 2.0]]], [[[102.0, 2.0], [103.0, 2.0], [103.0, 3.0], [102.0, 3.0], [102.0, 2.0]], [[102.0, 2.0], [103.0, 2.0], [103.0, 3.0], [102.0, 3.0], [102.0, 2.0]]]] } }
MongoDB .NET driver provides classes for both polygon types (GeoJsonPolygon<TCoordinates>, GeoJsonMultiPolygon<TCoordinates>). Both classes derive from GeoJsonGeometry<GeoJson2DCoordinates>. Furthermore you can use GeoJson2DCoordinates to represent your two-element arrays of doubles.
The driver will handle the rest - you can specify base abstract type as Geometry and the document will get deserialized to relevant concrete type in the runtime:
[BsonCollection("garda_subdistrict_boundaries")]
public class GardaSubdistrictBoundaryMongo : Document
{
[BsonElement("type")]
public string Type { get; set; }
[BsonElement("properties")]
public Properties Properties { get; set; }
[BsonElement("geometry")]
public GeoJsonGeometry<GeoJson2DCoordinates> Geometry { get; set; }
}
