C# asp .net 将数据库中数据变换为xml

   XmlDocument xmldoc;
            XmlNode xmlnode;
            XmlElement xmlelem;
            //1，创建到服务器同名目录下的xml文件：
            ////方法一：
            xmldoc = new XmlDocument();
            //加入XML的声明段落,<?xml version="1.0" encoding="gb2312"?>
            XmlDeclaration xmldecl;
            xmldecl = xmldoc.CreateXmlDeclaration("1.0", "gb2312", null);
            xmldoc.AppendChild(xmldecl);
            //加入一个根元素
            xmlelem = xmldoc.CreateElement("cross工程");
            xmlelem.SetAttribute("id", "0");//设置该节点id属性 
            xmlelem.SetAttribute("pid", "-1");//设置该节点pid属性 
            xmlelem.SetAttribute("typeId", "0");//设置该节点typeId属性 
            xmlelem.SetAttribute("nodeName", "cross工程");//设置该节点nodeName属性 
            xmldoc.AppendChild(xmlelem);
            Dictionary<string, string> dic = new Dictionary<string, string>();
            dic.Add("0", "cross工程");
            MySqlDataReader reader, read = null;
            MySqlParameter[] commandParameters = new MySqlParameter[] {
            };
            MySqlCommand sqlcom = new MySqlCommand();
            sqlcom.CommandText = "select * from treetable";
            read = reader = MySqlHelper.ExecuteReader(MySqlHelper.ConnectionStringManager, CommandType.Text, sqlcom.CommandText, commandParameters);
            while (reader.Read() == true)
            {

                string s = "//" + dic[reader["pid"].ToString()].ToString();
                XmlNode root = xmldoc.SelectSingleNode(s);//查找<Employees> 
                XmlElement xe1 = xmldoc.CreateElement(reader["nodeName"].ToString());//创建一个<Node>节点 
                xe1.SetAttribute("id", reader["id"].ToString());//设置该节点id属性 
                xe1.SetAttribute("pid", reader["pid"].ToString());//设置该节点pid属性 
                xe1.SetAttribute("typeId", reader["typeId"].ToString());//设置该节点typeId属性 
                xe1.SetAttribute("nodeName", reader["nodeName"].ToString());//设置该节点nodeName属性 
                dic.Add(reader["id"].ToString(), reader["nodeName"].ToString());
                root.AppendChild(xe1);//添加到<Employees>节点中 
            }
            xmldoc.Save("G:\\Test.xml");