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.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;

using System.Threading.Tasks;

​

​

// https://stackoverflow.com/questions/45358844/c-sharp-xml-serializer-deserializes-list-to-count-of-0-instead-of-null

​

​

    [XmlRootAttribute("MyClass", Namespace = "", IsNullable = false)]

    public class MyClass

    {

        private string comments;

        public string Comments

        {

            set { comments = value; }

            get { return comments; }

        }

​

        private System.Collections.Generic.List<string> tests = null;

​

        [XmlIgnore]

        public System.Collections.Generic.List<string> Tests

        {

            get { return tests; }

            set { tests = value; }

        }

​

        [XmlArray("Tests")]

        public string[] TestsArray

        {

            get

            {

                return (Tests == null ? null : Tests.ToArray());

            }

            set

            {

                if (value == null)

                    return;

                (Tests = Tests ?? new List<string>(value.Length)).AddRange(value);

            }

        }

    }

​

​

    class TestClass

    {

        public static void Test()

        {

            foreach (var tuple in GetXml())

                Test(tuple);

            Console.WriteLine("Tests complete.");

        }

​

        static void Test(Tuple<string, List<string>> tuple)

        {

            var xml = tuple.Item1;

​

            Console.WriteLine("Input XML: ");

            Console.WriteLine(xml);

​

            var myClass = xml.LoadFromXml<MyClass>();

​

            Console.WriteLine("myClass.Tests = {0}", myClass.Tests == null ? "null" : myClass.Tests.Count.ToString());

​

            Console.WriteLine("Re-serialized XML: ");

            Console.WriteLine(myClass.GetXml(true));

​

            Assert.IsTrue(ListsSame(myClass.Tests, tuple.Item2));

            Console.WriteLine("Contents of myClass.Tests are correct.\n");

        }

        static bool ListsSame<T>(ICollection<T> list1, ICollection<T> list2)

        {

            if (object.ReferenceEquals(list1, list2))

                return true;

            else if (object.ReferenceEquals(list1, null) || object.ReferenceEquals(list2, null))

                return false;

            return list1.SequenceEqual(list2);

        }

​

        static IEnumerable<Tuple<string, List<string>>> GetXml()

        {

            return new[]

            {

                Tuple.Create(@"<MyClass>

  <SomeNode>value</SomeNode>

</MyClass>", (List<string>)null),

​

                Tuple.Create(@"<MyClass>

</MyClass>", (List<string>)null),

​

                Tuple.Create(@"<MyClass>

  <SomeNode>value</SomeNode>

  <Tests />

</MyClass>", new List<string>()),

​

                Tuple.Create(@"<MyClass>

  <SomeNode>value</SomeNode>

  <Tests></Tests>, 

</MyClass>", new List<string>()),

​

           Tuple.Create(@"<MyClass>

  <SomeNode>value</SomeNode>

  <Tests>

    <string>hello</string>

    <string>goodbye</string>

  </Tests>

</MyClass>", new List<string> { "hello", "goodbye" }),

            };

        }

    }

    public static class XmlSerializationHelper

    {

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

        {

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

            T returnValue = default(T);

            using (StringReader reader = new StringReader(xmlString))

            {

                object result = serial.Deserialize(reader);

                if (result is T)

                {

                    returnValue = (T)result;

                }

            }

            return returnValue;

        }

​

        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 AssertionFailedException : System.Exception

    {

        public AssertionFailedException() : base() { }

​

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

    }

​

    public static class Assert

    {

        public static void IsTrue(bool value)

        {

            if (value == false)

                throw new AssertionFailedException("failed");

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            TestClass.Test();

        }

    }

​