當試圖序列化系統內建的型別之後，若試圖反序列化為 object 型別一定會引發錯誤，請問在 Main() 方法不修改的情況下，如何讓這段程式正常運作？

Serialize_Deserialize_Test.cs

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = "1234";

            string xml = SiteHelper.Serialize(s);
            object obj = SiteHelper.Deserialize<object>(xml);
        }
    }

    public static class SiteHelper
    {
        public static string Serialize(object o)
        {
            XmlSerializer ser = new XmlSerializer(o.GetType());
            StringBuilder sb = new StringBuilder();
            StringWriter writer = new StringWriter(sb);
            ser.Serialize(writer, o);
            return sb.ToString();
        }

        public static T Deserialize<T>(string s)
        {
            MemoryStream ms = new MemoryStream(Encoding.GetEncoding("UTF-16").GetBytes(s));
            
            XmlTextReader reader = new XmlTextReader(ms);
            reader.Normalization = false;

            XmlSerializer ser = new XmlSerializer(typeof(T));

            object obj = ser.Deserialize(reader);   // Exception happen!!

            return (T)obj;
        }
    }
}