Download .zip file in asp.net

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication16.WebForm1" %>





   


   

   

     
             
            onrowcommand="GridView1_RowCommand">
   
 
  
        CommandArgument='<%# Eval("filename") %>'  Text='<%# Eval("filename") %>' CommandName="cmd">Download
   
   
   
   
   
   

   

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 WebApplication16
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        string str;
        SqlCommand com;
        SqlDataAdapter sqlda;
        DataSet ds;

        protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
        {
            if (e.CommandName == "cmd")
            {
                string filename = e.CommandArgument.ToString();
                string path = MapPath("~/filename/" + filename);
                byte[] bts = System.IO.File.ReadAllBytes(path);
                Response.Clear();
                Response.ClearHeaders();
                Response.AddHeader("Content-Type", "Application/octet-stream");
                Response.AddHeader("Content-Length", bts.Length.ToString());
                Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
                Response.BinaryWrite(bts);
                Response.Flush();
                Response.End();
            }
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(strConnString);
            con.Open();
            str = "select * from  test";
            com = new SqlCommand(str, con);
            sqlda = new SqlDataAdapter(com);
            ds = new DataSet();
            sqlda.Fill(ds,"test");
            GridView1.DataMember = "test";
            GridView1.DataSource = ds;
            GridView1.DataBind();
            con.Close();

        }

        protected void Button2_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(strConnString);
            con.Open();
            str = "select * from test where id = '" + TextBox1.Text + "'";
            com = new SqlCommand(str, con);
            sqlda = new SqlDataAdapter(com);
            ds = new DataSet();
            sqlda.Fill(ds, "test");
            con.Close();
            GridView1.DataSource = ds;
            GridView1.DataMember = "test";
            GridView1.DataBind();
        }
    }
}