using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

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/74274082/newtonsoft-json-different-null-handling-values-for-serialization-and-deseriali?noredirect=1#comment131129868_74274082

​

    public class IgnoreNullValuesWhenDeserializingRootConverter : JsonConverter

    {

        // Disables the converter in a thread-safe manner to prevent a stack overflow as the converter calls itself.

        [ThreadStatic]

        static bool disabled;

        bool Disabled { get { return disabled; } set { disabled = value; } }

​

        public override bool CanWrite => false;

        public override bool CanRead => !Disabled;

        public override bool CanConvert(Type objectType) => !Disabled;

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) 

        {

            using (new PushValue<bool>(true, () => Disabled, val => Disabled = val))

            using (new PushValue<NullValueHandling>(NullValueHandling.Ignore, () => serializer.NullValueHandling, val => serializer.NullValueHandling = val))

            {

                return serializer.Deserialize(reader, objectType);

            }

        }

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) => throw new NotImplementedException();

    }

​

    public struct PushValue<T> : IDisposable

    {

        Action<T> setValue;

        T oldValue;

​

        public PushValue(T value, Func<T> getValue, Action<T> setValue)

        {

            if (getValue == null || setValue == null)

                throw new ArgumentNullException();

            this.setValue = setValue;

            this.oldValue = getValue();

            setValue(value);

        }

​

        #region IDisposable Members

​

        // By using a disposable struct we avoid the overhead of allocating and freeing an instance of a finalizable class.

        public void Dispose() => setValue?.Invoke(oldValue);

​

        #endregion

    }

​

    public class Model

    {

        int? nullableIntValue = 101;

        string stringValue = "i was not nulled out";

        public string StringValue

        {

            get

            {

                //Console.WriteLine("Getter for {0} called", nameof(StringValue));

                return stringValue;

            }

            set

            {

                Console.WriteLine("Setter for {0} called", nameof(StringValue));

                stringValue = value;

            }

        }

​

        public int? NullableIntValue

        {

            get

            {

                //Console.WriteLine("Getter for {0} called", nameof(IntValue));

                return nullableIntValue;

            }

            set

            {

                Console.WriteLine("Setter for {0} called", nameof(NullableIntValue));

                nullableIntValue = value;

            }

        }

        public string ShouldBeNull { get; set; }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var json = @"{""StringValue"":null, ""NullableIntValue"" : null}";

            var options = new 

            {

                SerializerSettings = new JsonSerializerSettings(),

            };

​

            options.SerializerSettings.Converters.Add(new IgnoreNullValuesWhenDeserializingRootConverter()); //Ignore null values when deserializing

            options.SerializerSettings.NullValueHandling = NullValueHandling.Include; // Do not ignore null values when serializing

            var model = JsonConvert.DeserializeObject<Model>(json, options.SerializerSettings);

            var json2 = JsonConvert.SerializeObject(model, options.SerializerSettings);

            Console.WriteLine("Input JSON: {0}", json);

            Console.WriteLine("Re-serialized {0}: {1}", model, json2);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

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

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​