#region 根据xml节点 查询xml节点的值并作修改
/// <summary>
/// 根据xml节点 查询xml节点的值并作修改
/// </summary>
/// <param name="fileName">要加载的xml文件</param>
/// <param name="tagName">xml节点的名称</param>
/// <param name="newXmlText">修改后的值</param>
/// <returns></returns>
public void GetXmlbySelNodel(string fileName, string selNodeName, string tagName,string newXmlText)
{
  try
  {
   doc.Load(Server.MapPath(fileName));
   XmlNodeList nodelist = doc.DocumentElement.SelectSingleNode(selNodeName).ChildNodes;
   foreach (XmlNode node in nodelist)
   {
    XmlElement xle = node as XmlElement;
    XmlNodeList list = xle.ChildNodes;
    for (int j = 0; j < list.Count; j++) {
     if (xle.ChildNodes[j].Name == tagName) {
      xle.ChildNodes[j].InnerText = newXmlText;
      SaveXml(fileName);
      break;
     }
    }
   }
  }
  catch { 
  }
}
#endregion
#region 保存修改后xml文件内容
//保存修改后xml文件内容
public void SaveXml(string fileName)
{
  doc.Save(Server.MapPath(fileName));
}
#endregion
string selNodeName="//url/data";
string fileName = "meituanAPI.xml";
GetXmlbySelNodel(fileName, selNodeName, "website", "编程素材网");
GetXmlbySelNodel(fileName, selNodeName, "siteurl", "www.1sucai.cn");
GetXmlbySelNodel(fileName, selNodeName, "city", "杭州");
GetXmlbySelNodel(fileName, selNodeName, "tip", "送ipad 抽奖!!");
GetXmlbySelNodel(fileName, "//data/shops", "name", "上海洲信 信息技术有限公司!");
DataSet ds = new DataSet();
ds.ReadXml(Server.MapPath("meituanAPI.xml"));
XmlTextWriter writer = new XmlTextWriter(Response.OutputStream, Response.ContentEncoding);
ds.Tables[0].WriteXml(writer);
Response.ContentType = "text/xml;charset=gb2312";
Response.Flush();
Response.End()

Response.ClearContent();
Response.ClearHeaders();
Response.contentType="application/xml"';
Response.WriterFile(Server.Mappath("API/54tuanAPI.xml"));
Response.Flush();
Response.End();