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.ComponentModel;

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

​

#nullable enable

​

    public class DictionaryTupleConverter<T1, T2, TValue> : JsonConverter<Dictionary<(T1, T2), TValue>>

    {

        readonly Tuple2Converter<T1, T2> tupleConverter = new ();

        public override Dictionary<(T1, T2), TValue>? ReadJson(JsonReader reader, Type objectType, Dictionary<(T1, T2), TValue>? existingValue, bool hasExistingValue, JsonSerializer serializer)

        {

            var innerDictionary = serializer.Deserialize<Dictionary<string, TValue>>(reader);

            if (innerDictionary == null)

                return null;

            var dictionary = existingValue ?? (Dictionary<(T1, T2), TValue>)serializer.ContractResolver.ResolveContract(objectType)!.DefaultCreator()!;

            foreach (var pair in innerDictionary)

                dictionary.Add(((T1, T2))tupleConverter.ConvertFromInvariantString(pair.Key)!, pair.Value);

            return dictionary;

        }

​

        public override void WriteJson(JsonWriter writer, Dictionary<(T1, T2), TValue>? value, JsonSerializer serializer) => 

            serializer.Serialize(writer, value!.ToDictionary(p => tupleConverter.ConvertToInvariantString(p.Key)!, p => p.Value));

    }

​

    public class Tuple2Converter<T1, T2> : TypeConverter {

        public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType) {

            return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);

        }

​

        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value) {

            var parts = Convert.ToString(value)!.Trim('(').Trim(')').Split(",");

            var item1 = (T1)TypeDescriptor.GetConverter(typeof(T1)).ConvertFromInvariantString(parts[0].Trim())!;

            var item2 = (T2)TypeDescriptor.GetConverter(typeof(T2)).ConvertFromInvariantString(parts[1].Trim())!;

            return (item1, item2);

        }

        public override object? ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type destinationType)

        {

            // There's no tuple.ToInvariantString() method so we have to do this ourselves.

            if (destinationType == typeof(string) && value is ValueTuple<T1, T2> tuple)

            {

                var s1 = TypeDescriptor.GetConverter(typeof(T1)).ConvertToInvariantString(tuple.Item1)!;

                var s2 = TypeDescriptor.GetConverter(typeof(T2)).ConvertToInvariantString(tuple.Item2)!;

                return string.Format("({0},{1})", s1, s2);

            }

            return base.ConvertTo(context, culture, value, destinationType);

        }

    }

​

    public static class TypeExtensions

    {

        public static IEnumerable<Type> GetInterfacesAndSelf(this Type type)

            => (type ?? throw new ArgumentNullException()).IsInterface ? new[] { type }.Concat(type.GetInterfaces()) : type.GetInterfaces();

​

        public static IEnumerable<Type []> GetDictionaryKeyValueTypes(this Type type)

            => type.GetInterfacesAndSelf().Where(t => t.IsGenericType && t.GetGenericTypeDefinition() == typeof(IDictionary<,>)).Select(t => t.GetGenericArguments());

​

        public static Type []? GetDictionaryKeyValueType(this Type type)

        {

            var types = type.GetDictionaryKeyValueTypes().ToList();

            return types.Count == 1 ? types[0] : null;

        }

​

        public static IEnumerable<Type> BaseTypesAndSelf(this Type? type)

        {

            while (type != null)

            {

                yield return type;

                type = type.BaseType;

            }

        }

        public static T ThrowOnNull<T>(this T? value) where T : class => value ?? throw new ArgumentNullException();

    }

​

    public class MyClass

    {

        public string? Value { get; set; }

    }

​

    class TestClass

    {

        public static void Test()

        {

            int n = 2;

            var d = (from i in Enumerable.Range(0, n)

                     from j in Enumerable.Range(0, n)

                     select ((i, j), new MyClass { Value = (i+j).ToString() }))

                .ToDictionary(p => p.Item1, p => p.Item2);

            var settings = new JsonSerializerSettings

            {

                Converters = { new DictionaryTupleConverter<int, int, MyClass>() },

            };

            var json = JsonConvert.SerializeObject(d, Formatting.Indented, settings);

            Console.WriteLine(json);

            var d2 = JsonConvert.DeserializeAnonymousType(json, d, settings);

​

            var json2 = JsonConvert.SerializeObject(d2, Formatting.Indented, settings);

            Assert.AreEqual(json, json2);

            Assert.AreEqual(d.Count(), d2!.Count());

        }   

    }

​

    public static partial class JsonExtensions

    {

        public static JsonReader AssertTokenType(this JsonReader reader, JsonToken tokenType) => 

            reader.TokenType == tokenType ? reader : throw new JsonSerializationException(string.Format("Unexpected token {0}, expected {1}", reader.TokenType, tokenType));

        public static JsonReader ReadToContentAndAssert(this JsonReader reader) =>

            reader.ReadAndAssert().MoveToContentAndAssert();

​

        public static JsonReader MoveToContentAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.

                reader.ReadAndAssert();

            while (reader.TokenType == JsonToken.Comment) // Skip past comments.

                reader.ReadAndAssert();

            return reader;

        }

​

        public static JsonReader ReadAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (!reader.Read())

                throw new JsonReaderException("Unexpected end of JSON stream.");

            return reader;

        }

    }

​

    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;

            }

        }

    }

​