using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NetTopologySuite;

using NetTopologySuite.Geometries;

using NetTopologySuite.IO;

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/66771338/how-do-i-configure-a-custom-converter-that-returns-json-instead-of-a-string-in

​

    public class MyModel

    {

        public NetTopologySuite.Geometries.Polygon poly { get; set; }

    }

​

    public class MyPolygonConverter : JsonConverter<Polygon>

    {

        public override void WriteJson(JsonWriter writer, Polygon value, JsonSerializer serializer)

        {

            var geoJsonSerializer = NetTopologySuite.IO.GeoJsonSerializer.Create();

            geoJsonSerializer.Serialize(writer, value);

        }

        public override Polygon ReadJson(JsonReader reader, Type objectType, Polygon existingValue, bool hasExistingValue, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var model = new MyModel

            {

                poly = new Polygon(new LinearRing(new[]

                                                  {

                                                      new Coordinate(-100, 45),

                                                      new Coordinate(-98, 45),

                                                      new Coordinate(-99, 46),

                                                      new Coordinate(-100, 45),

                                                  }))

            };

​

            var serializer = NetTopologySuite.IO.GeoJsonSerializer.CreateDefault(

                new JsonSerializerSettings

                {

                    ReferenceLoopHandling = ReferenceLoopHandling.Ignore,

                    NullValueHandling = NullValueHandling.Ignore,

                    Formatting = Formatting.Indented, // Or none, if you prefer

                });

            var sb = new StringBuilder();

            using (var sw = new StringWriter(sb))

            using (var jsonWriter = new JsonTextWriter(sw))

                serializer.Serialize(jsonWriter, model);

​

            var geoJson = sb.ToString();

            Console.WriteLine(geoJson);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Assembly.GetName().Name,  typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​