C# simple operation on xml

<?xml version="1.0" encoding="utf-8"?>  
<userdata createuser="false">  
<dataconnection>  
<server>localhost</server>  
<uid>sa</uid>  
<pwd></pwd>  
</dataconnection>  
<net>  
<name>jiayuan</name>  
</net>  
</userdata>

XmlDocument doc=new XmlDocument();  
doc.Load("config.xml");//可以再加入路径：如D:\config.xml  
XmlNode xnuser=doc.SelectSingleNode("userdata");  
string flag=xnuser.Attributes["createuser"].InnerText;

XmlDocument doc=new XmlDocument();  
doc.Load("config.xml");  
XmlNode xnserver = doc.SelectSingleNode("userdata/dataconnection/server");

XmlDocument doc=new XmlDocument();  
doc.Load("config.xml");  
XmlNode xnuser=doc.SelectSingleNode("userdata");  
xnuser.Attributes["createuser"].InnerText="false";  
doc.Save("config.xml");

XmlDocument doc = new XmlDocument();  
XmlTextReader reader = new XmlTextReader("config.xml");  
doc.Load("config.xml");  
XmlElement root = doc.DocumentElement; // 获取根节点  
XmlElement tagMessage = doc.CreateElement("net");  
XmlElement tagText = doc.CreateElement("name");  
tagText.InnerText = netname;  
tagMessage.AppendChild(tagText); // 追加到 xml 文本的最后面  
root.AppendChild(tagMessage);  
reader.Close(); // 关闭 XmlTextReader  
doc.Save("config.xml"); // 保存 xml 文件