实例：增删改查

using System;using System.Collections.Generic;using System.Text;using System.Xml;namespace ConsoleApp1{    public class XMLHelper    {        public void Add()        {            XmlDocument doc = new XmlDocument();            doc.Load("XMLFile1.xml");            var root = doc.DocumentElement;            var newnode = doc.CreateNode("element", "student", "");                      var newnode1 = doc.CreateNode("element", "sno", "");            newnode1.InnerText = "4";            var newnode2 = doc.CreateNode("element", "sname", "");            newnode2.InnerText = "成龙";            newnode.AppendChild(newnode1);            newnode.AppendChild(newnode2);            root.AppendChild(newnode);            doc.Save("XMLFile1.xml");                    }        public void Delete()        {            XmlDocument doc = new XmlDocument();            doc.Load("XMLFile1.xml");            var root = doc.DocumentElement;            root.RemoveChild(root.FirstChild);                        doc.Save("XMLFile1.xml");        }        public void Update()        {            XmlDocument doc = new XmlDocument();            doc.Load("XMLFile1.xml");            var root = doc.DocumentElement;            var first = root.FirstChild.FirstChild;            first.InnerText = "fffffffffff";            doc.Save("XMLFile1.xml");        }        public void GetNodes()        {            XmlDocument doc = new XmlDocument();            doc.Load("XMLFile1.xml");            var root = doc.DocumentElement;            var find = root.ChildNodes[1].InnerText;            Console.WriteLine(find);        }        public void GetOneNodeByName()        {            XmlDocument doc = new XmlDocument();            doc.Load("XMLFile1.xml");            var root = doc.DocumentElement;            foreach (XmlElement item in root.ChildNodes)            {                if(item.FirstChild.InnerText == "4")                {                    Console.WriteLine(item.OuterXml);                }            }        }    }}