Export Gridview to Exel file

create new website and add Default page and in it add Gridview and button

In Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
GridView1.DataSource = BindData();
GridView1.DataBind();
}
}

private string ConnectionString
{

get { return @"Data Source=YASER\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"; }

}

private DataSet BindData()
{
// make the query
string query = "SELECT * FROM Products";
SqlConnection myConnection = new SqlConnection(ConnectionString);
SqlDataAdapter ad = new SqlDataAdapter(query, myConnection);
DataSet ds = new DataSet();
ad.Fill(ds, "Products");
return ds;

}

protected void Button1_Click(object sender, EventArgs e)
{
Response.Clear();

Response.AddHeader("content-disposition", "attachment;filename=FileName.xls");

Response.Charset = "";

// If you want the option to open the Excel file without saving than

// comment out the line below

// Response.Cache.SetCacheability(HttpCacheability.NoCache);

Response.ContentType = "application/vnd.xls";

System.IO.StringWriter stringWrite = new System.IO.StringWriter();

System.Web.UI.HtmlTextWriter htmlWrite =
new HtmlTextWriter(stringWrite);

GridView1.RenderControl(htmlWrite);

Response.Write(stringWrite.ToString());

Response.End();

}

public override void VerifyRenderingInServerForm(Control control)
{

// Confirms that an HtmlForm control is rendered for the
//specified ASP.NET server control at run time.

}
}