Convert GridView To Document or Excel

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.Data.SqlClient;

using System.IO;

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

{

   SqlConnection con = new SqlConnection("Data Source=AAPTI-A20B83733\\SQLEXPRESS;Initial Catalog=NewLogin;Integrated Security=True");

   protected void Page_Load(object sender, EventArgs e)

   {

       SqlDataAdapter da = new SqlDataAdapter("select * from LoginDetails", con);

       DataSet ds = new DataSet();

       da.Fill(ds);

       GridView1.DataSource = ds;

       GridView1.DataBind();

   }

   protected void Button1_Click(object sender, EventArgs e)

   {

       

       string fileName = "attachment;filename= ExampleDOC.doc";

       Response.ClearContent();

       Response.AddHeader("content-disposition", fileName);

       Response.ContentType = "application/doc";

       StringWriter sw = new StringWriter();

       HtmlTextWriter hw = new HtmlTextWriter(sw);

       GridView1.RenderControl(hw);

       Response.Write(sw.ToString());

       Response.End();

   }

   public override void VerifyRenderingInServerForm(Control control)

   {

      

   }

}