<Code File:
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class InsertXML : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
       
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        DataSet ds = new DataSet();
        ds.ReadXml(MapPath("XMLFile.xml"));
        DataRow dr = ds.Tables[0].NewRow();
        dr[0] = TextBox1.Text;
        dr[1] = TextBox2.Text;
        dr[2] = TextBox3.Text;
        dr[3] = TextBox4.Text;
        ds.Tables[0].Rows.Add(dr);
        ds.WriteXml(MapPath("XMLFile.xml"));
        Label1.Text = "Record is inserted";
     }
}