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 System.Text.Json;

using System.Text.Json.Serialization;

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/71689776/convert-jsonconverter-to-system-text-json-to-support-multiple-primitive-types-an

​

#nullable enable

​

    public class RoundingJsonConverter : RoundingJsonConverterBase

    {

        // The converter works for float, double & decimal.  Max number of decimals for double is 15, for decimal is 28, so throw an exception of numberOfDecimals > 28.

        public RoundingJsonConverter(int numberOfDecimals) => NumberOfDecimals = (numberOfDecimals < 0 || numberOfDecimals > 28 ? throw new ArgumentOutOfRangeException(nameof(numberOfDecimals)) : numberOfDecimals);

        protected override int NumberOfDecimals { get; }

    }

​

    public class RoundingTo2DigitsJsonConverter : RoundingJsonConverterBase

    {

        protected override int NumberOfDecimals { get; } = 2;

    }

​

    public class RoundingTo6DigitsJsonConverter : RoundingJsonConverterBase

    {

        protected override int NumberOfDecimals { get; } = 6;

    }

    public abstract class RoundingJsonConverterBase : JsonConverter<object>

    {

        protected abstract int NumberOfDecimals { get; }

        public override object Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

        {

            typeToConvert = Nullable.GetUnderlyingType(typeToConvert) ?? typeToConvert;

            if (typeToConvert == typeof(decimal))

                return reader.GetDecimal();

            else if (typeToConvert == typeof(double))

                return reader.GetDouble();

            else if (typeToConvert == typeof(float))

                return (float)reader.GetDouble();

            throw new NotImplementedException();

        }

​

        public override void Write(Utf8JsonWriter writer, object value, JsonSerializerOptions options)

        {

            switch (value)

            {

                case double d:

                    writer.WriteNumberValue(Math.Round(d, Math.Min(15, NumberOfDecimals)));

                break;

                case decimal d:

                    writer.WriteNumberValue(Math.Round(d, NumberOfDecimals));

                break;

                case float f:

                    writer.WriteNumberValue((decimal)Math.Round((decimal)f, NumberOfDecimals));

                break;

                default:

                    throw new NotImplementedException();

            }

        }

        public override bool CanConvert(Type typeToConvert)

        {

            typeToConvert = Nullable.GetUnderlyingType(typeToConvert) ?? typeToConvert;

            return typeToConvert == typeof(double) || typeToConvert == typeof(decimal) || typeToConvert == typeof(float);

        }           

    }

​

    public class Model

    {

        public double d { get; set; }

        public double? nd { get; set; }

        public float f { get; set; }

        public float? nf { get; set; }

        public decimal dc { get; set; }

        public decimal ndc { get; set; }

​

        [JsonConverter(typeof(RoundingTo6DigitsJsonConverter))]

        public decimal? SixDecimalPlaceValue { get; set; }

    }

​

    class TestClass

    {

        public static void Test()

        {

            Test(4, 1.8888888888888888888888888888888888M);

            Test(4, 2M);

            foreach (var i in Enumerable.Range(0, 28))

                Test(i);

            Assert.Throws<ArgumentOutOfRangeException>(() => Test(29));

        }

​

        static void Test(int numberOfDigits)

        {

            Test(numberOfDigits, 1.1111111111111111111111111111111111M);

        }

        static void Test(int numberOfDigits, decimal value)

        {

            var model = new Model

            {

                d = (double)value,

                nd = (double)value,

                f = (float)value,

                nf = (float)value,

                dc = value,

                ndc = value,

                SixDecimalPlaceValue = value,

            };

            var options = new JsonSerializerOptions

            {

                Converters = { new RoundingJsonConverter(numberOfDigits) },

                WriteIndented = true,

            };

            var json = JsonSerializer.Serialize(model, options);

            Console.WriteLine(json);

        }

    }

​

    public class Program

    {

        public static void Main()

        {

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

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

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return "";

        }

    }

​