Export Gridview Record to Excel in C#

Coding:

=> Demo.aspx Source code

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Demo.aspx.cs" Inherits="architecture.Demo" %>

<!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></title>
</head>
<body>
<form id="form1" runat="server">
<div> <br /> <br />
<asp:GridView ID="gvlist" runat="server" AutoGenerateColumns="false" CellPadding="4" ForeColor="#333333">
<Columns>
<asp:BoundField DataField="ID" HeaderText="Id" HeaderStyle-Width="200px" />
<asp:BoundField DataField="FirstName" HeaderText="First Name" HeaderStyle-Width="200px" />
<asp:BoundField DataField="LastName" HeaderText="Last Name" HeaderStyle-Width="200px" /> </Columns>
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" /> </asp:GridView> <br />
<asp:Button ID="btnExport" runat="server" OnClick="Button1_Click" Text="Export To Excel" /> </div> <br /> </br>
</form>
</body>
</html>

=>Demo.aspx.cs code behind file

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Configuration;
using System.Data.SqlClient;
using System.IO;
using System.Collections;
namespace architecture
{
public partial class Demo: System.Web.UI.Page
{
SqlConnection con;
DataTable dt;
//Connection String from Web.config file
public static string constr = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
protected void Page_Load(object sender, EventArgs e) {
//lblTime.Text = DateTime.Today.DayOfWeek.ToString();
if (!IsPostBack) {
ShowData();
}
}
//method for Displaying Data in Gridview
protected void ShowData()
{
SqlConnection con = new SqlConnection(constr);
string str = "Select * from TbDemo; select * from TbDemo";
con.Open();
SqlCommand cmd = new SqlCommand(str, con);
DataTable dt = new DataTable();
SqlDataReader reader = cmd.ExecuteReader();
dt.Load(reader);
DataView dv = dt.DefaultView;
gvlist.DataSource = dv;
gvlist.DataBind();
int i = 0;
con.Close();
}
protected void Button1_Click(object sender, EventArgs e)
{
Response.ClearContent();
Response.AddHeader("content-disposition", "attachment;filename=Users.xls");
Response.ContentType = "applicatio/excel";
StringWriter sw = new StringWriter();;
HtmlTextWriter htm = new HtmlTextWriter(sw);
gvlist.RenderControl(htm);
Response.Write(sw.ToString());
Response.End();
}
public override void VerifyRenderingInServerForm(Control control) {}
}
}