xml add

           XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load("bookstore.xml");
            XmlNode root = xmlDoc.SelectSingleNode("bookstore");//查找<bookstore>  
            XmlElement xe1 = xmlDoc.CreateElement("book");//创建一个<book>节点  
            xe1.SetAttribute("genre", "红");//设置该节点genre属性  
            xe1.SetAttribute("ISBN", "4");//设置该节点ISBN属性  

            XmlElement xesub1 = xmlDoc.CreateElement("title");
            xesub1.InnerText = "精通";//设置文本节点  
            xe1.AppendChild(xesub1);//添加到<book>节点中  
            XmlElement xesub2 = xmlDoc.CreateElement("author");
            xesub2.InnerText = "捷";
            xe1.AppendChild(xesub2);
            XmlElement xesub3 = xmlDoc.CreateElement("price");
            xesub3.InnerText = "58.3";
            xe1.AppendChild(xesub3);
            root.AppendChild(xe1);//添加到<bookstore>节点中  
            xmlDoc.Save("bookstore.xml");