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 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/54550629/newtonsoft-json-net-jsonconverter-attribute-preserve-references-issue-when-deser

    public class CustomJsonConverter : Newtonsoft.Json.JsonConverter

    {

        [ThreadStatic]

        static bool disabled;

​

        // Disables the converter in a thread-safe manner.

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

​

        public override bool CanWrite { get { return !Disabled; } }

​

        public override bool CanRead { get { return !Disabled; } }

​

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

        {

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

            using (new PushValue<PreserveReferencesHandling>(PreserveReferencesHandling.Objects, () => serializer.PreserveReferencesHandling, val => serializer.PreserveReferencesHandling = val))

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

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

            {

                serializer.Serialize(writer, value);

            }

        }

​

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

        {

            if (reader.TokenType == JsonToken.Null)

            {

                return null;

            }

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

            using (new PushValue<PreserveReferencesHandling>(PreserveReferencesHandling.Objects, () => serializer.PreserveReferencesHandling, val => serializer.PreserveReferencesHandling = val))

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

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

            {

                return serializer.Deserialize(reader, objectType);

            }

        }

​

        public override bool CanConvert(Type objectType)

        {

            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);

        }

​

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

        public void Dispose()

        {

            if (setValue != null)

                setValue(oldValue);

        }

    }

​

    [JsonConverter(typeof(CustomJsonConverter))]

    public abstract class ModelBase : IModelBase

    {

        public string ID { get; set; }

        public DateTime CreatedAt { get; set; }

        public DateTime ModifiedAt { get; set; }

    }

​

    public class CustomerModel : ModelBase

    {

        public string Name { get; set; }

        public UserModel CreatedBy { get; set; }

        public UserModel ModifiedBy { get; set; }

    }

​

    public class UserModel : ModelBase

    {

        public string Name { get; set; }

        public UserModel CreatedBy { get; set; }

        public UserModel ModifiedBy { get; set; }

    }

​

    public interface IModelBase

    {

    }

​

    class TestClass

    {

        public static void Test()

        {

            TestDeserialize();

        }

​

        static object Deserialize(Stream streamFromWebAPICall, Type objectType)

        {

            using (var sr = new StreamReader(streamFromWebAPICall))

            {

                using (var jtr = new JsonTextReader(sr))

                {

                    var settings = new JsonSerializerSettings

                    {

                        DefaultValueHandling = DefaultValueHandling.Ignore,

                        NullValueHandling = NullValueHandling.Ignore,

                    };

​

                    var js = JsonSerializer.CreateDefault(settings);

                    return js.Deserialize(jtr, objectType);

                }

            }

        }

​

        static void TestDeserialize()

        {

            var inputJson = GetInputJson();

​

            var streamFromWebAPICall = new MemoryStream(Encoding.UTF8.GetBytes(inputJson));

​

            var root = (List<CustomerModel>)Deserialize(streamFromWebAPICall, typeof(List<CustomerModel>));

​

            var settings = new JsonSerializerSettings

            {

                DefaultValueHandling = DefaultValueHandling.Ignore,

                NullValueHandling = NullValueHandling.Ignore,

            };

            var outputJson = JsonConvert.SerializeObject(root, Formatting.Indented, settings);

​

            Console.WriteLine("Round-tripped {0}:", root);

            Console.WriteLine(outputJson);

​

            Assert.IsTrue(JToken.DeepEquals(JToken.Parse(inputJson), JToken.Parse(outputJson)));

            Assert.IsTrue(root.Count == 2 && root[1].CreatedBy == root[0].CreatedBy && root[1].ModifiedBy == root[0].CreatedBy);

        }

​

        static string GetInputJson()

        {

            var json = @"[

    {

        ""$id"": ""1"",

        ""Name"": ""Customer1"",

        ""CreatedBy"": {

            ""$id"": ""2"",

            ""ID"": ""1"",

            ""Name"": ""User1""

        },

        ""ModifiedBy"": {

            ""$id"": ""3"",

            ""ID"": ""3"",

            ""Name"": ""User3""

        },

        ""ID"": ""1"",

        ""CreatedAt"": ""2019-02-06T00:00:04"",

        ""ModifiedAt"": ""2019-02-06T00:20:12""

    },

    {

        ""$id"": ""4"",

        ""Name"": ""Customer2"",

        ""CreatedBy"": {

            ""$ref"": ""2""

        },

        ""ModifiedBy"": {

            ""$ref"": ""2""

        },

        ""ID"": ""2"",

        ""CreatedAt"": ""2019-02-06T00:10:00"",

        ""ModifiedAt"": ""2019-02-06T00:10:00""

    }

]";

            return json;

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​