using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Xml.Serialization;

using System.Xml;

using System.IO;

using System.Diagnostics;

using System.Collections.ObjectModel;

using System.Threading;

using System.ComponentModel;

using System.Xml.Linq;

using System.Reflection;

using System.Data;

using System.Xml.Schema;

using System.Text.RegularExpressions;

using System.Net;

using System.Xml.XPath;

using System.Globalization;

using System.ComponentModel.DataAnnotations;

using System.Collections;

using System.Runtime.InteropServices;

using System.Runtime.Serialization;

​

    // https://stackoverflow.com/questions/47571925/c-how-to-hide-a-field-which-is-used-only-for-xml-serialization-retrocompatibil

​

​

    [System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple = false)]

    public class XmlUnknownElementEventHandlerAttribute : System.Attribute

    {

    }

​

    public static partial class XmlSerializationHelper

    {

        public static T LoadFromXml<T>(this string xmlString, XmlSerializer serial = null)

        {

            serial = serial ?? new XmlSerializer(typeof(T));

            serial.UnknownElement += UnknownXmlElementEventHandler;

            using (StringReader reader = new StringReader(xmlString))

            {

                return (T)serial.Deserialize(reader);

            }

        }

        public static void UnknownXmlElementEventHandler(object sender, XmlElementEventArgs e)

        {

            var obj = e.ObjectBeingDeserialized;

​

            foreach (var method in obj.GetType().BaseTypesAndSelf()

                .SelectMany(t => t.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly))

                .Where(m => Attribute.IsDefined(m, typeof(XmlUnknownElementEventHandlerAttribute))))

            {

                method.Invoke(obj, BindingFlags.Public | BindingFlags.NonPublic, null, new object[] { sender, e }, null);

            }

        }

    }

​

    public static class TypeExtensions

    {

        public static IEnumerable<Type> BaseTypesAndSelf(this Type type)

        {

            while (type != null)

            {

                yield return type;

                type = type.BaseType;

            }

        }

    }

​

    public partial class MyClass

    {

        public string MyValue { get; set; }

    }

​

    public partial class MyClass

    {

        [XmlUnknownElementEventHandler]

        public void HandleOldElement(object sender, XmlElementEventArgs e)

        {

            if (e.Element.Name == "OldValue")

            {

                Console.WriteLine("{0}: processed property {1} with value {2}", this, e.Element.Name, e.Element.OuterXml);

                MyValue = "Old value was: " + e.Element.InnerText;

            }

        }

    }

​

    public class DerivedClass : MyClass

    {

        public string DerivedValue { get; set; }

​

        [XmlUnknownElementEventHandler]

        public void HandleOldDerivedElement(object sender, XmlElementEventArgs e)

        {

            if (e.Element.Name == "OldDerivedProperty")

            {

                Console.WriteLine("{0}: processed property {1} with value {2}", this, e.Element.Name, e.Element.OuterXml);

                DerivedValue = "Old value was: " + e.Element.InnerText;

            }

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            Test<MyClass>(GetOldMyClassXml(), GetNewExpectedMyClassXml());

            Test<DerivedClass>(GetOldDerivedXml(), GetNewExpectedDerivedXml());

​

            Console.WriteLine("\nAll tests passed.");

        }

​

        private static void Test<T>(string xmlString, string expectedXml)

        {

            Console.WriteLine("\nOld XML: ");

            Console.WriteLine(xmlString);

​

            var model = xmlString.LoadFromXml<T>();

            var xml2 = model.GetXml(true);

​

            Console.WriteLine("Deserialized and re-serialized {0}:", model);

            Console.WriteLine(xml2);

​

            Assert.IsTrue(XNode.DeepEquals(XElement.Parse(expectedXml), XElement.Parse(xml2)));

            Console.WriteLine("Re-serialized XML is as expected.");

        }

​

        static string GetNewExpectedDerivedXml()

        {

            var xml = @"<DerivedClass>

  <MyValue>Old value was: Hello</MyValue>

  <DerivedValue>Old value was: Hello Again</DerivedValue>

</DerivedClass>";

            return xml;

        }

​

        static string GetOldDerivedXml()

        {

            var xml = @"<DerivedClass><OldValue>Hello</OldValue><OldDerivedProperty>Hello Again</OldDerivedProperty></DerivedClass>";

            return xml;

        }

​

        static string GetOldMyClassXml()

        {

            var xml = @"<MyClass><OldValue>Hello</OldValue></MyClass>";

            return xml;

        }

​

        static string GetNewExpectedMyClassXml()

        {

            var xml = @"<MyClass>

  <MyValue>Old value was: Hello</MyValue>

</MyClass>";

            return xml;

        }

    }

​

    public class AssertionFailedException : System.Exception

    {

        public AssertionFailedException() : base() { }

​

        public AssertionFailedException(string s) : base(s) { }

    }

​

    public static class Assert

    {

        public static void IsTrue(bool value)

        {

            IsTrue(value, "failed");

        }

​

        public static void IsTrue(bool value, string message)

        {

            if (value == false)

                throw new AssertionFailedException(message ?? "failed");

        }

    }

​

    public static partial class XmlSerializationHelper

    {

        public static string GetXml<T>(this T obj, bool omitStandardNamespaces)

        {

            return obj.GetXml(null, omitStandardNamespaces);

        }

        public static string GetXml<T>(this T obj, XmlSerializer serializer = null, bool omitStandardNamespaces = false)

        {

            XmlSerializerNamespaces ns = null;

            if (omitStandardNamespaces)

            {

                ns = new XmlSerializerNamespaces();

                ns.Add("", ""); // Disable the xmlns:xsi and xmlns:xsd lines.

            }           

            using (var textWriter = new StringWriter())

            {

                var settings = new XmlWriterSettings() { Indent = true }; // For cosmetic purposes.

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

                    (serializer ?? new XmlSerializer(obj.GetType())).Serialize(xmlWriter, obj, ns);

                return textWriter.ToString();

            }

        }

    }

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine();

​

            TestClass.Test();

        }

    }

​