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;

        }