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 Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

    // https://stackoverflow.com/questions/48179763/force-decimal-type-in-class-definition-during-serialization

​

    class TestData

    {

        [JsonConverter(typeof(FloatParseHandlingConverter), FloatParseHandling.Decimal)]

        public List<Row> rows;

    }

​

    // this class is being used by other APIs.

    class Row

    { 

        public string myString { get; set; }

        // this will have int, string, 'decimal' types. Decimal type gets auto converted to Double and gets rounded

        public List<dynamic> values { get; set; } 

    }

​

​

    public class FloatParseHandlingConverter : JsonConverter

    {

        readonly FloatParseHandling floatParseHandling;

​

        public FloatParseHandlingConverter(FloatParseHandling floatParseHandling)

        {

            this.floatParseHandling = floatParseHandling;

        }

​

        public override bool CanConvert(Type objectType)

        {

            throw new NotImplementedException();

        }

​

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

        {

            if (reader.TokenType == JsonToken.Null)

                return null;

            var old = reader.FloatParseHandling;

            try

            {

                reader.FloatParseHandling = floatParseHandling;

                existingValue = existingValue ?? serializer.ContractResolver.ResolveContract(objectType).DefaultCreator();

                serializer.Populate(reader, existingValue);

                return existingValue;

            }

            finally

            {

                reader.FloatParseHandling = old;

            }

        }

​

        public override bool CanWrite { get { return false; } }

​

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

        {

            throw new NotImplementedException();

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var test = new TestData

            {

                rows = new List<Row>

                {

                    new Row

                    {

                        myString = "hello",

                        values = new List<object> { 1.010101010101010101010101m, 2020.202020202020202020202m, 123456789012345678.90123456m, "hello" },

                    }

                }

            };

            Console.WriteLine("\ntest.rows[].values types: {0}.", String.Join(",", test.rows.SelectMany(r => r.values).Select(i => i.GetType().Name)));

​

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

​

            Console.WriteLine("\nSerialized JSON: ");

            Console.WriteLine(json);

​

            var test2 = JsonConvert.DeserializeObject<TestData>(json);

​

            Console.WriteLine("\ntest2.rows[].values types: {0}.", String.Join(",", test2.rows.SelectMany(r => r.values).Select(i => i.GetType().Name)));

​

            Assert.IsTrue(test2.rows.SelectMany(r => r.values).SequenceEqual(test.rows.SelectMany(r => r.values)), "values are not equal!");

            Assert.IsTrue(test2.rows.SelectMany(r => r.values).Select(i => i.GetType()).SequenceEqual(test.rows.SelectMany(r => r.values).Select(i => i.GetType())), "types are not equal!");

            Assert.IsTrue(!test2.rows.SelectMany(r => r.values).OfType<double>().Any(), "doubles found!");

​

            Console.WriteLine("All tests passed.\n");

        }

    }

    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;

            }

        }

    }

​

    public class AssertionFailedException : System.Exception

    {

        public AssertionFailedException() : base() { }

​

        public AssertionFailedException(string s) : base(s) { }

    }

​

    public static class Assert

    {

        public static void IsTrue(bool value)

        {

            IsTrue(value, "failed");

        }

​

        public static void IsTrue(bool value, string message)

        {

            if (value == false)

                throw new AssertionFailedException(message ?? "failed");

        }

    }

​