下面的内容请放到Page_Load事件中,并需求导入命名空间using System.Xml ;

   //创建Xml文档
   XmlDocument doc1 = new XmlDocument();

   //加载Xml结构
   doc1.LoadXml("<ReturnString><Result/><TransactionID/><Description/></ReturnString>");

   //为各个结点进行赋值
   doc1.GetElementsByTagName("Result")[0].InnerText = "1";
   doc1.GetElementsByTagName("TransactionID")[0].InnerText ="123";
   doc1.GetElementsByTagName("Description")[0].InnerText = "这是一个测试";

   //输出数据
   Response.Write ( doc1.OuterXml);