在现有xml增加一个新的节点

 XmlDocument xml = new XmlDocument();
                    xml.Load(Server.MapPath("~/etao/IncrementIndex.xml"));
                
                    XmlNode item_ids = xml.GetElementsByTagName("item_ids")[0];
                    XmlElement newElement = xml.CreateElement("outer_id");
                    newElement.SetAttribute("action", "upload");
                    newElement.InnerText =pid;
                    item_ids.AppendChild(newElement);
                    XmlNodeList modified = xml.GetElementsByTagName("modified");
                    modified.Item(0).InnerText = DateTime.Now.ToString();
                    xml.Save(Server.MapPath("~/etao/IncrementIndex.xml"));

xml:

 <?xml version="1.0" encoding="utf-8" ?> 
- <root>
  <version>1.0</version> 
  <modified>2011-7-4 9:42:54</modified> 
  <seller_id>官网</seller_id> 
  <cat_url>etao/SellerCats.xml</cat_url> 
  <dir>etao/item/</dir> 
- <item_ids>
  <outer_id action="upload">ID1000018452</outer_id> 
 //新增加的
  <outer_id action="upload">ID1000018413</outer_id> 
 
  </item_ids>
  </root>