XmlUtil.cs

using System;
using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace Util
{
    public static class XmlUtil
    {
        public static XmlDocument SerializeToDocument(object input, string xmlNamespace = null)
        {
            if (input == null) throw new ArgumentNullException(nameof(input));

            var xmlSerializer = new XmlSerializer(input.GetType(), xmlNamespace);

            XmlDocument xmlDocument;

            using (var memoryStream = new MemoryStream())
            {
                xmlSerializer.Serialize(memoryStream, input);

                memoryStream.Position = 0;

                var settings = new XmlReaderSettings {IgnoreWhitespace = true};

                using (var xmlReader = XmlReader.Create(memoryStream, settings))
                {
                    xmlDocument = new XmlDocument();
                    xmlDocument.Load(xmlReader);
                }
            }

            return xmlDocument;
        }

        public static T DeserializeToObject<T>(string input)
        {
            if (input == null) throw new ArgumentNullException(nameof(input));

            var xmlSerializer = new XmlSerializer(typeof(T));
            var byteArray = Encoding.UTF8.GetBytes(input);
            using (var stream = new MemoryStream(byteArray))
            {
                return (T)xmlSerializer.Deserialize(stream);
            }
        }
    }
}