XML C#

//http://facebooktoolkit.codeplex.com/
//http://facebooktoolkit.codeplex.com/license
using System.Collections.Generic;
using System.Text;
namespace Facebook.Utility
{
    /// 
    /// Helper functions for string manipulation
    /// 

    public static class StringHelper
    {
        /// 
        /// Strip Non Valid XML Characters.
        /// 

        public static string StripNonValidXMLCharacters(string s)
        {
            StringBuilder _validXML = new StringBuilder(s.Length, s.Length); // Used to hold the output.
            char[] charArray = s.ToCharArray();
            if (string.IsNullOrEmpty(s)) return string.Empty; // vacancy test.
            for (int i = 0; i < charArray.Length; i++)
            {
                char current = charArray[i];
                if ((current == 0x9) ||
                (current == 0xA) ||
                (current == 0xD) ||
                ((current >= 0x20) && (current <= 0xD7FF)) ||
                ((current >= 0xE000) && (current <= 0xFFFD)))
                    _validXML.Append(current);
            }
            return _validXML.ToString();
        }
   }
}