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

​

//https://stackoverflow.com/questions/61061584/ignoring-some-default-values-for-serialization

​

    public enum Flavor : ulong { ValueNotSet, Cherry, Blueberry, Cheese }

​

    public class DanishInventory { public int QtyInStock; public Flavor Flavor; }

​

    public class EnumDefaultValueContractResolver : DefaultContractResolver

    {

        protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)

        {

            var property = base.CreateProperty(member, memberSerialization);

            if (property.DefaultValueHandling == null)

            {

                if (property.PropertyType.IsEnum)

                {

                    //For safety you could check here if the default value is named ValueNotSet and only set IgnoreAndPopulate in that case.

                    //var defaultValue = Enum.ToObject(property.PropertyType, 0);

                    //if (defaultValue.ToString() == "ValueNotSet")

                    //{                 

                        property.DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate; // Or DefaultValueHandling.Ignore if you prefer

                    //}

                }

            }

​

            return property;

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var resolver = new EnumDefaultValueContractResolver();

            var settings = new JsonSerializerSettings { ContractResolver = resolver };

            foreach (Flavor flavor in Enum.GetValues(typeof(Flavor)))

            {

                var inventory  = new DanishInventory { Flavor = flavor };

                var json = JsonConvert.SerializeObject(inventory, settings);

​

                Console.WriteLine("json for Flavor={0}", json);

                var test2 = JsonConvert.DeserializeObject<DanishInventory>(json, settings);

                Assert.IsTrue((flavor == default(Flavor)) == !json.Contains(nameof(inventory.Flavor)));

                Assert.IsTrue(inventory.Flavor == test2.Flavor);

            }

        }   

    }

​

    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.CodeBase.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;

        }

    }

​