最近在做项目，这几天遇到的问题要用到几个数据转换，特此记录一下。

        public static string DataTableToXml(this DataTable dt)
        {
            ////第一种  返回的XML字符串比较干净，DataTable行中数据为空的没有写入到XML字符串中
            System.IO.TextWriter tw = new System.IO.StringWriter();
            dt.WriteXml(tw);
            return tw.ToString();
            
            ////第二种  同第一种
            MemoryStream ms = null;
            XmlTextWriter XmlWt = null;
            ms = new MemoryStream();
            ////根据ms实例化XmlWt
            XmlWt = new XmlTextWriter(ms, Encoding.Unicode);
            ////获取ds中的数据
         dt.WriteXml(XmlWt);
            int count = (int)ms.Length;
            byte[] temp = new byte[count];
            ms.Seek(0, SeekOrigin.Begin);
            ms.Read(temp, 0, count);
            ////返回Unicode编码的文本
        UnicodeEncoding ucode = new UnicodeEncoding();
            string returnValue = ucode.GetString(temp).Trim();
            return returnValue;
            

            ///第三种   返回的XML字符串比较复杂，包括了DataTable中各个Column的定义，以及字段类型,当然还包括DataTable行值，以及其他属性
            StringBuilder sb = new StringBuilder();
            XmlWriter writer = XmlWriter.Create(sb);
            XmlSerializer serializer = new XmlSerializer(typeof(DataTable));
            serializer.Serialize(writer, dt);
            writer.Close();
            return sb.ToString();


        }

        public static DataSet XMLToDataTable(this string StrData)
        {
            if (!string.IsNullOrEmpty(StrData))
            {
                XmlDocument xmlDoc = new XmlDocument();
                DataSet ds = new DataSet();
                try
                {
                    xmlDoc.LoadXml(StrData);
                    ds.ReadXml(GetStream(xmlDoc.OuterXml));
                    return ds;
                }
                catch (Exception e)
                {
                    throw e;
                }
            }
            else
            {
                return null;
            }
        }

        public static StreamReader GetStream(this string xmlStr)
        {
            byte[] tempByte = Encoding.UTF8.GetBytes(xmlStr);
            MemoryStream stream = new MemoryStream(tempByte);
            //stream.Position = 0;
            StreamReader streamReader = new StreamReader(stream);
            return streamReader;
        }

DataTable dt= new DataTable("Test");
string  XmlData=dt.DataTableToXml();

string XmlData="此处为XML字符串";
DataTable dt=XmlData.XMLToDataTable().Tables["Test"];