XML in C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml;
using System.Xml.XPath;
namespace WebApplication1
{
   public partial class _Default : System.Web.UI.Page
   {
       protected void Page_Load(object sender, EventArgs e)
       {

       }

       protected void Button1_Click(object sender, EventArgs e)
       {
           XmlTextWriter writer = new XmlTextWriter("G:\\new4.xml",
System.Text.Encoding.Default);
writer.WriteStartDocument();
//creating the name of the main node
writer.WriteStartElement("menu");
writer.WriteStartElement("RECORD");
writer.WriteStartElement("First");
writer.WriteString("Mahesh");
writer.WriteEndElement();
writer.WriteEndElement();
writer.WriteStartElement("RECORD");
writer.WriteStartElement("First");
writer.WriteString("nikhil");
writer.WriteEndElement();
writer.WriteEndElement();
writer.Close();

       }

       protected void Button2_Click(object sender, EventArgs e)
       {
           // Create xml dom
          XmlDocument XMLDom = new XmlDocument();
          //load your xml file
          XMLDom.Load(@"g:/new4.xml");
          XmlNode root = XMLDom.DocumentElement;
          XmlNode childNode = XMLDom.CreateNode(XmlNodeType.Element,
"RECORD", "");
          XmlElement newbook = XMLDom.CreateElement("First");
          newbook.InnerText = "saurabh";
          //XmlElement newbook2 = XMLDom.CreateElement("Second");
          //newbook2.InnerText = "mittal";
          childNode.AppendChild(newbook);
          root.AppendChild(childNode);
          XMLDom.Save("g:/new4.xml");

       }

       protected void Button3_Click(object sender, EventArgs e)
       {
           // Select childnode where you want to modify data. The
following step "PNode" is parent node and "Node1" is the one which you
want to update the data
           // Create xml dom
           // Create xml dom
           XmlDocument XMLDom = new XmlDocument();
           //load your xml file
           XMLDom.Load(@"g:/new4.xml");

           XmlNodeList newXMLNodes = XMLDom.SelectNodes("/menu/RECORD/First");
           foreach (XmlNode newXMLNode in newXMLNodes)
               //Updating data where "Node1" is "sree" with "kambham"
               if (newXMLNode.InnerText == "Mahesh")
                //to modify
                   newXMLNode.InnerText = "meena";
                   //to delete
                 //  newXMLNode.ParentNode.RemoveChild(newXMLNode);
           XMLDom.Save("g:/new4.xml");
           XMLDom = null;
           //The above step updates xml file where ever it finds
"sree" with "kambham"
       }
   }
}