using System;

using System.Collections.Generic;

using System.Text;

using System.Linq;

using System.Xml.Serialization;

using System.Runtime.Serialization;

using System.Xml;

using System.Xml.Linq;

using System.IO;

using System.Data;

using System.Runtime.Serialization;

using System.Runtime.Serialization.Formatters.Binary;

using System.IO.Compression;

using System.Reflection;

​

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

​

//https://stackoverflow.com/questions/68671856/how-to-add-property-to-dto-in-a-backward-compatible-way

​

    namespace VOld

    {

        [Serializable]

        public class TestClass

        {

            private string firstProperty;

​

            [XmlAttribute]

            public string FirstProperty

            {

                get => firstProperty;

                set => firstProperty = value;

            }

        }

    }

​

    namespace VNew

    {

        [Serializable]

        public class TestClass

        {

            private string firstProperty;

​

            [OptionalField]

            private string secondProperty;

​

            [XmlAttribute]

            public string FirstProperty

            {

                get => firstProperty;

                set => firstProperty = value;

            }

​

            [XmlAttribute]

            public string SecondProperty

            {

                get => secondProperty;

                set => secondProperty = value;

            }

        }

    }

​

    public static partial class DataContractSerializerHelper

    {

        public static string ToContractXml<T>(this T obj, DataContractSerializer serializer = null, XmlWriterSettings settings = null)

        {

            serializer = serializer ?? new DataContractSerializer(obj == null ? typeof(T) : obj.GetType());

            using (var textWriter = new StringWriter())

            {

                settings = settings ?? new XmlWriterSettings { Indent = true };

                using (var xmlWriter = XmlWriter.Create(textWriter, settings))

                {

                    serializer.WriteObject(xmlWriter, obj);

                }

                return textWriter.ToString();

            }

        }

​

        public static T FromContractXml<T>(string xml, DataContractSerializer serializer = null)

        {

            using (var textReader = new StringReader(xml ?? ""))

            using (var xmlReader = XmlReader.Create(textReader))

            {

                return (T)(serializer ?? new DataContractSerializer(typeof(T))).ReadObject(xmlReader);

            }

        }

    }

​

    public class TestClass

    {

        public static void Test()

        {

            var oldToNew = DataContractSerializerHelper.FromContractXml<VNew.TestClass>(GetOldXml());

            oldToNew.Dump();

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

            var xml2 = DataContractSerializerHelper.ToContractXml(oldToNew);

            Console.WriteLine(xml2);

​

            var newToOld =  DataContractSerializerHelper.FromContractXml<VOld.TestClass>(GetNewXmlForOld());

            newToOld.Dump();

        }

        static string GetOldXml() => @"<TestClass xmlns:i=""http://www.w3.org/2001/XMLSchema-instance"" xmlns=""http://schemas.datacontract.org/2004/07/VNew"">

  <firstProperty>first value</firstProperty>

</TestClass>";

        static string GetNewXmlForOld() => @"<TestClass xmlns:i=""http://www.w3.org/2001/XMLSchema-instance"" xmlns=""http://schemas.datacontract.org/2004/07/VOld"">

  <firstProperty>first value</firstProperty>

  <secondProperty i:nil=""true"" />

</TestClass>";

    }

​

    public class Program

    {

        public static void Main()

        {

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

            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.CodeBase.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;

        }

    }

​