Disable Enable LinkButton while downloading file in ASP.Net

Hi

i have 2 linkbuttons. one which i will be using for downloading file and uploading after editing the downloading the file from db.

I want to disable link button after download untill another linkbutton is used for uploading.

Linkbutton doesn't seem to disable.

I want to disable download button while download and enable it after upload.

Please Help.

            SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["connString"].ConnectionString);
            DisableLinkButton(btndown);
            string filename, contentType;
            txtDownload.Text = tvBookContent.SelectedNode.Value;
            txtchap.Text= tvBookContent.SelectedNode.Text.ToString(); 
            if(txtchap.Text=="Installation of ACS 235 V UHF-1 SYSTEM" || txtchap.Text== "Installation of ACS 235-LH V UHF 1 TRANSCEIVER" || txtchap.Text== "Installation of V UHF-1 ANTENNA 12-200")
            {
                using (ZipFile zip = new ZipFile())
                {
                    zip.AlternateEncodingUsage = ZipOption.AsNecessary;
                    string[] filePaths = Directory.GetFiles(Server.MapPath("~/File/"));
                    SqlCommand cmd = new SqlCommand("select tbn.vcFilePath,tbn.Rawdata_img,tbn.Rawdata_tbl_xml,tbn.FileName,tbn.Rawfilename_img,tbn.Rawfilename_tbl from tblBookNodes_IPC tbn inner join tblModule tbm on tbn.iModuleId=tbm.iModuleId where tbm.vcModuleTitle='" + txtDownload.Text.ToString() + "'", conn);
                    conn.Open();
                    using (SqlDataReader dr = cmd.ExecuteReader())
                    {
                        while (dr.Read())
                        {
                            byte[] bytes = (byte[])dr["vcFilePath"];
                            byte[] bytes_img = (byte[])dr["Rawdata_img"];
                            byte[] bytes_tbl = (byte[])dr["Rawdata_tbl_xml"];
                            string flname = dr["FileName"].ToString();
                            string filename_img = dr["Rawfilename_img"].ToString();
                            string filename_tbl = dr["Rawfilename_tbl"].ToString();
                            zip.AddEntry(flname, bytes);
                            zip.AddEntry(filename_img, bytes_img);
                            zip.AddEntry(filename_tbl, bytes_tbl);
                        }
                    }
                    conn.Close();
                    Response.Clear();
                    Response.BufferOutput = false;
                    string zipName = String.Format("Zip_{0}.zip", DateTime.Now.ToString("yyyy-MMM-dd-HHmmss"));
                    Response.ContentType = "application/zip";
                    Response.AddHeader("content-disposition", "attachment; filename=" + zipName);
                    zip.Save(Response.OutputStream);
                    Response.End();
                    ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Download Sucessfull');", true);
                }
            }
             else
            { 
                SqlCommand cmd1 = new SqlCommand("select tbn.Rawdata,tbn.Rawfilename from tblBookNodes_AMM tbn inner join tblModule tbm on tbn.iModuleId=tbm.iModuleId where tbm.iModuleId='" + txtDownload.Text.ToString() + "'", conn);
                conn.Open();
                SqlDataReader dr = cmd1.ExecuteReader();
                if (dr.Read())
                {
                    byte[] bytes = (byte[])dr["Rawdata"];
                    contentType = ".xml";
                    filename = dr["Rawfilename"].ToString();
                    conn.Close();
                    Response.Clear();
                    Response.Buffer = true;
                    Response.Charset = "";
                    Response.Cache.SetCacheability(HttpCacheability.NoCache);
                    Response.ContentType = contentType;
                    Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename);
                    Response.BinaryWrite(bytes);
                    Response.Flush();
                    Response.End();
                    
                    Response.Write(" < script > alert('Download successfully') </ script > ");
                }
            }

        public static void DisableLinkButton(LinkButton btndown)
        {
            btndown.Attributes.Remove("href");
            btndown.Attributes.CssStyle[HtmlTextWriterStyle.Color] = "gray";
            btndown.Attributes.CssStyle[HtmlTextWriterStyle.Cursor] = "default";
            if (btndown.Enabled != false)
            {
                btndown.Enabled = false;
            }

            if (btndown.OnClientClick != null)
            {
                btndown.OnClientClick = null;
            }
        }

Thanks