1、将DataTable转换成xml字符串
　　　　　　//将DataTable转换成xml字符串:
        public string ConvertDataTableToXml(DataTable dt)
        {
            MemoryStream stream = null;
            XmlTextWriter writer = null;
            try
            {
                stream = new MemoryStream();
                writer = new XmlTextWriter(stream, System.Text.Encoding.Unicode);
                dt.WriteXml(writer);
                int count = (int)stream.Length;
                byte[] arr = new byte[count];
                stream.Seek(0, SeekOrigin.Begin);
                stream.Read(arr, 0, count);
                System.Text.Encoding ucode = System.Text.Encoding.Unicode;    //若使用utf-8，遇中文会发生乱码
                return ucode.GetString(arr).Trim();
            }
            catch
            {
                return String.Empty;
            }
        }

//将xml转换为字符串
private String XmlDocToString(XmlDocument xmlDoc, String EncodeName)  //GBK
        {
            MemoryStream xmlstream = new MemoryStream();
            XmlTextWriter writer = new XmlTextWriter(xmlstream, Encoding.GetEncoding(EncodeName));
            writer.Formatting = Formatting.Indented;
            xmlDoc.Save(writer);
            StreamReader sr = new StreamReader(xmlstream, Encoding.GetEncoding(EncodeName));
            xmlstream.Position = 0;
            String strResult = sr.ReadToEnd();
            sr.Close();
            xmlstream.Close();
            writer.Close();
            return strResult;
        }