学步园

代码：

using System.Xml;
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        XmlDocument doc = new XmlDocument();
        doc.Load(Server.MapPath("data.xml"));
        XmlNode node = doc.DocumentElement;
        XmlNode book = node.SelectSingleNode ( "//book[@id='01']" );
        XmlElement bookName = doc.CreateElement ( "name" );
        bookName.InnerText = "Xiyouji";
        XmlAttribute numbers = doc.CreateAttribute ("numbers");
        numbers.Value = "100";
        bookName.Attributes.Append ( numbers );
        book.AppendChild ( bookName );
        doc.Save ( Server.MapPath ( "data.xml" ) );
    }
}
结果：

<?xml version="1.0" encoding="gb2312"?>
<root>
  <library>
    <book id="01">
      <name numbers="100">Xiyouji</name>
    </book>
    <book id="02">
      <name numbers="100">Hongloumeng</name>
    </book>
  </library>
</root>