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/72536967/newtonsoft-json-how-can-i-choose-the-constructor-to-deserialize-based-on-passe

​

    // The following class cannot be changed

​

    public class Test<T, U> where U : struct

    {

        public Test(T firstProperty)

        {

            FirstProperty = firstProperty;

        }

​

        public Test(U secondProperty)

        {

            SecondProperty = secondProperty;

        }

​

        public T FirstProperty { get; }

​

        public U SecondProperty { get; }

    }

​

    class TestConverter<T, U> : JsonConverter where U : struct

    {

        // Here we make use of the {PropertyName}Specified pattern to track which properties actually got deserialized.

        // https://stackoverflow.com/questions/39223335/how-to-force-newtonsoft-json-to-serialize-all-properties-strange-behavior-with/

        class TestDTO

        {

            public T FirstProperty { get; set; }

            [JsonIgnore] public bool FirstPropertySpecified { get; set; }

            public U SecondProperty { get; set; }

            [JsonIgnore] public bool SecondPropertySpecified { get; set; }

        }

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

        {

            var dto = serializer.Deserialize<TestDTO>(reader);

            if (dto == null)

                return null;

            else if (dto.FirstPropertySpecified && !dto.SecondPropertySpecified)

                return new Test<T, U>(dto.FirstProperty);

            else if (!dto.FirstPropertySpecified && dto.SecondPropertySpecified)

                return new Test<T, U>(dto.SecondProperty);

            else

                throw new InvalidOperationException(string.Format("Wrong number of properties specified for {0}", objectType));

        }

​

        public override bool CanConvert(Type objectType) => objectType == typeof(Test<T, U>);

        public override bool CanWrite => false;

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

    }

​

    public class TestContractResolver : DefaultContractResolver

    {

        protected override JsonObjectContract CreateObjectContract(Type objectType)

        {

            var contract = base.CreateObjectContract(objectType);

            if (objectType.IsGenericType && objectType.GetGenericTypeDefinition() == typeof(Test<,>))

                contract.Converter = (JsonConverter)Activator.CreateInstance(typeof(TestConverter<,>).MakeGenericType(objectType.GetGenericArguments()));

            return contract;

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var json1 = @"{""FirstProperty"":""hello""}";

            var json2 = @"{""SecondProperty"": 10101}";

            var json3 = @"{}";

            var json4 = @"{""FirstProperty"":""hello"", ""SecondProperty"": 10101}";

​

            IContractResolver resolver = new TestContractResolver(); // Cache this statically for best performance

            var settings = new JsonSerializerSettings

            {

                ContractResolver = resolver,

            };

            var test1 = JsonConvert.DeserializeObject<Test<string, long>>(json1, settings);

            test1.Dump();

            Assert.AreEqual(test1.FirstProperty, "hello");

            var test2 = JsonConvert.DeserializeObject<Test<string, long>>(json2, settings);

            test2.Dump();

            Assert.AreEqual(test2.SecondProperty, 10101L);

            Assert.Throws<InvalidOperationException>(() => JsonConvert.DeserializeObject<Test<string, long>>(json3, settings));

            Assert.Throws<InvalidOperationException>(() => JsonConvert.DeserializeObject<Test<string, long>>(json4, settings));

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

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

            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;

            }

        }

    }

​