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/66309150/how-do-i-write-a-float-like-82-0-with-the-0-intact-using-utf8jsonwriter

​

    public class DoubleConverter : JsonConverter<double>

    {

        public override double Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) => 

            reader.GetDouble();

​

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

        {

            if ((value % 1) == 0)

            {

                // Convert to decimal with one digit

                var s = value.ToString("F1", NumberFormatInfo.InvariantInfo);

                try

                {

                    var d = decimal.Parse(s, NumberFormatInfo.InvariantInfo);

                    writer.WriteNumberValue(d);

                }

                catch (Exception e)

                {

                    Console.WriteLine("Value {0} threw exception {1}", s, e.Message);

                    throw;

                }

            }

            else

            {

                writer.WriteNumberValue(value);

            }

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var doubles = new []

            {

                82.0,

                82.1,

                7e27,

                78e27,

                (double)(0.99m*decimal.MaxValue),

                0, 1, 2,

                -82.0,

                double.Epsilon,

                long.MaxValue,

                double.MinValue,

                double.MaxValue,

            };

            foreach (var d in doubles)

            {

                var options = new JsonSerializerOptions

                {

                    Converters = { new DoubleConverter() },

                    WriteIndented = true,

                };

                var json1 = JsonSerializer.Serialize(d);

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

                Console.WriteLine("Original JSON = {0}, fixed JSON = {1}", json1, 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 null;

        }

    }

​