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/64913477/c-sharp-system-text-json-rounds-doubles-during-serialization

​

    class TestClass

    {

        public static void Test()

        {

            double d = 99.6;

            var json = JsonSerializer.Serialize(d);

            Console.WriteLine(json);

            var d2 = JsonSerializer.Deserialize<double>(json);

            Assert.AreEqual(d, d2);

            var json2 = JsonSerializer.Serialize(d2);

            Console.WriteLine(json2);

​

            var d3 = JsonSerializer.Deserialize<double>(json2);

​

            Assert.AreEqual(d, d3);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), 64bit = {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion(), Environment.Is64BitOperatingSystem);

            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;

        }

    }

​