Convert any serializable object in XML

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

public static string GetXmlFromObject(object objItem, string rootAttribute)
        {
            XmlSerializer xmlSer;
            XmlSerializerNamespaces xmlNs = new XmlSerializerNamespaces();
            MemoryStream memStream = new MemoryStream();

            xmlNs.Add("", "");

            xmlSer = new XmlSerializer(objItem.GetType(), new XmlRootAttribute(rootAttribute));
            xmlSer.Serialize(memStream, objItem, xmlNs);

            string xmlString = ASCIIEncoding.UTF8.GetString(memStream.ToArray(), 0, memStream.ToArray().Length);
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(xmlString);
            if (xmlDoc.SelectSingleNode(rootAttribute) != null)
                return xmlDoc.SelectSingleNode(rootAttribute).OuterXml;

            return string.Empty;
        }