how to store the datagirdview values into database table please help...

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Insert_data_from_Gridview_database._Default" %>

DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

<head runat="server">

    <title>Untitled Pagetitle>

head>

<body>

    <form id="form1" runat="server">

    <div>

    <asp:Label ID="Label1" runat="server" Text="">asp:Label>

    <asp:GridView ID="GridView1" runat="server">

    asp:GridView>

    <asp:Button ID="btn_insert" runat="server" onclick="btn_insert_Click"

        Text="Insert Records" />

    <asp:Button ID="btn_show" runat="server" onclick="btn_show_Click"

        style="height: 26px" Text="Show Records" />

    div>

    form>

body>

html>

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;

using System.Data.SqlClient;

namespace Insert_data_from_Gridview_database

{

    public partial class _Default : System.Web.UI.Page

    {

        string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

        SqlCommand com;

        protected void btn_show_Click(object sender, EventArgs e)

        {

            DataSet reportData = new DataSet();

            reportData.ReadXml(Server.MapPath("student.xml"));

            GridView1.DataSource = reportData;

            GridView1.DataBind();

        }

        protected void btn_insert_Click(object sender, EventArgs e)

        {

            foreach (GridViewRow g1 in GridView1.Rows)

            {

                SqlConnection con = new SqlConnection(connStr);

                com = new SqlCommand("insert into student(sid,sname,smarks,saddress) values ('" + g1.Cells[0].Text + "','" + g1.Cells[1].Text + "','" + g1.Cells[2].Text + "','" + g1.Cells[3].Text + "')", con);

                con.Open();

                com.ExecuteNonQuery();

                con.Close();

            }

            Label1.Text = "Records inserted successfully";

        }

    }

}