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/71709697/newtonsoft-json-converts-datetime-format-when-deserializing-to-string

​

    public class MyData

    {

        [JsonConstructor]

        public MyData(string value, string startDate, string endDate)

        {

            this.Value = value;

            this.StartDate = startDate;

            this.EndDate = endDate;

        }

​

        public string Value { get; }

        public string StartDate { get; }

        public string EndDate { get; }

    }

    class TestClass

    {

        public static void Test()

        {

            var json = GetJson();

            var jsonFilePath = @"Question71709697.json";

            File.WriteAllText(jsonFilePath, json);

            var jsonSettings = new JsonSerializerSettings();

            jsonSettings.DateFormatHandling = DateFormatHandling.IsoDateFormat;

            jsonSettings.DateFormatString = "yyyy-MM-ddTHH:mm:ss.fffffffZ";

            jsonSettings.DateParseHandling = DateParseHandling.DateTimeOffset;

            jsonSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;

​

            MyData myData;

            using (FileStream fileStream = File.OpenRead(jsonFilePath))

            using (StreamReader streamReader = new StreamReader(fileStream))

            using (JsonTextReader jsonReader = new JsonTextReader(streamReader))

            {

                myData = (MyData)JsonSerializer.CreateDefault(jsonSettings).Deserialize(jsonReader, typeof(MyData));

            }           

            Console.WriteLine($"myData.StartDate={myData.StartDate}, myData.EndDate={myData.EndDate}");

​

            // I had to add the following to ensure that MyData would be reserialized witb the same casing as the original JSON.

            jsonSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();

​

            var json2 = JsonConvert.SerializeObject(myData, Formatting.Indented, jsonSettings);

​

            Console.WriteLine("Re-serialized {0}:", myData);

            Console.WriteLine(json2);

            // Assert that the original and re-serialized JSON are identical

            Assert.AreEqual(json, json2);

        }   

        static string GetJson() => @"{

  ""value"": ""someData"",

  ""startDate"": ""2021-01-16T00:00:00.000Z"",

  ""endDate"": ""2021-01-18T00:00:00.000Z""

}";

    }

​

    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;

            }

        }

    }

​

    public static partial class JsonExtensions

    {

        public static JsonReader AssertTokenType(this JsonReader reader, JsonToken tokenType) => 

            reader.TokenType == tokenType ? reader : throw new JsonSerializationException(string.Format("Unexpected token {0}, expected {1}", reader.TokenType, tokenType));

        public static JsonReader ReadToContentAndAssert(this JsonReader reader) =>

            reader.ReadAndAssert().MoveToContentAndAssert();

​

        public static JsonReader MoveToContentAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.

                reader.ReadAndAssert();

            while (reader.TokenType == JsonToken.Comment) // Skip past comments.

                reader.ReadAndAssert();

            return reader;

        }

​

        public static JsonReader ReadAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (!reader.Read())

                throw new JsonReaderException("Unexpected end of JSON stream.");

            return reader;

        }

    }

​

​