Having trouble serializing NetTopologySuite FeaturesCollection to GeoJSON

Question

Trying to return some pretty simple GeoJSON data. I found NetTopologySuite, and set up a simple FeaturesCollection and tried to serialize it out to a GeoJson string only to get the following error:

"Self referencing loop detected for property 'CoordinateValue' with type 'GeoAPI.Geometries.Coordinate'. Path 'Features[0].Geometry.Coordinates[0]'."

Looking through the class headers, Point uses Coordinate, which does have a Coordinate property so I can see why there would be a circular reference. The thing is, most (if not all) the Geometries seem to use Point, so that would make it impossible to ever serialize anything... unless I'm missing something.

So is this a bug or am I missing something?

Tested with just a Point and got the same error, so here's the code for that:

using NTS = NetTopologySuite;

var ret = new NTS.Geometries.Point(42.9074, -78.7911);

var jsonSerializer = NTS.IO.GeoJsonSerializer.Create();

var sw = new System.IO.StringWriter();
jsonSerializer.Serialize(sw, ret);

var json = sw.ToString();

What is this `Create()` method? I don't see it [here](https://github.com/NetTopologySuite/NetTopologySuite/blob/d6b9737798d2ed4d85864f04b9689bc4ff193344/NetTopologySuite.IO/NetTopologySuite.IO.GeoJSON/GeoJsonSerializer.cs). — dbc, Nov 05 '14 at 19:16
If you are using a modified constructor for `GeoJsonSerializer`, you need to make sure a [`CoordinateConverter`](https://github.com/NetTopologySuite/NetTopologySuite/blob/d6b9737798d2ed4d85864f04b9689bc4ff193344/NetTopologySuite.IO/NetTopologySuite.IO.GeoJSON/Converters/CoordinateConverters.cs) is passed to it, as is shown [here](https://github.com/NetTopologySuite/NetTopologySuite/blob/d6b9737798d2ed4d85864f04b9689bc4ff193344/NetTopologySuite.IO/NetTopologySuite.IO.GeoJSON/GeoJsonSerializer.cs). — dbc, Nov 05 '14 at 19:29
Create() is part of the parent class (apparently.) Switching to the default constructor works perfectly. Feel free to make that an actual answer and I'll mark it. :) — CodeRedick, Nov 05 '14 at 19:36

dbc · Accepted Answer · 2019-07-27T00:59:07.600

Update

GeoJsonSerializer has been moved to NetTopologySuite.IO.GeoJSON and now has its own static Create() method:

/// <summary>
/// Factory method to create a (Geo)JsonSerializer
/// </summary>
/// <remarks>Calls <see cref="GeoJsonSerializer.CreateDefault()"/> internally</remarks>
/// <returns>A <see cref="JsonSerializer"/></returns>
public new static JsonSerializer Create()
{
    return CreateDefault();
}

Use of the direct constructor has been deprecated:

[Obsolete("Use GeoJsonSerializer.Create...() functions")]
public GeoJsonSerializer() : this(Wgs84Factory) { }

The code in the question should now work as expected.

Original Answer

Use the default constructor for the GeoJsonSerializer class:

var jsonSerializer = new NetTopologySuite.IO.GeoJsonSerializer();

That attaches a CoordinateConverter which prevents the problem.

GeoJsonSerializer does not actually have a static Create() method, so you are falling back on the base class's JsonSerializer.Create(). In fact the following would have resulted in a compiler error:

GeoJsonSerializer jsonSerializer = NTS.IO.GeoJsonSerializer.Create();

score 0 · Answer 2 · answered Dec 16 '15 at 17:46

0

Instead of returning Json after you have serialized already, you can use :

        return Content(sw.ToString, "application/Json");

answered Dec 16 '15 at 17:46

Takudzwa Mawarire

95
3
17

Ahmed Alejo · Answer 3 · 2020-03-09T04:38:18.823

A bit late to the party but here is my take on this: you can easily easily make the Point compatible with your current Json Serializer settings.

[DataContract]
public class GeoLocation : NetTopologySuite.Geometries.Point
{
    const int GoogleMapsSRID = 4326 ;

    public GeoLocation(double latitude, double longitude)
        : base(x: longitude, y: latitude) =>
          base.SRID = GoogleMapsSRID;

    [DataMember]
    public double Longitude => base.X;

    [DataMember]
    public double Latitude => base.Y;
}

The DataContract and DataMember are key here:

new GeoLocation(42.9074, -78.7911).ToJson() => {"longitude":42.9074,"latitude":-78.7911}

Having trouble serializing NetTopologySuite FeaturesCollection to GeoJSON

3 Answers3

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