Zip Folder is always corrupted after downloaded

protected void gvFiles_RowCommand(object sender, System.Web.UI.WebControls.GridViewCommandEventArgs e)
        {
            string fileUrl = String.Empty;

            if(e.CommandName.Equals("DownloadFile"))
            {
                fileUrl = e.CommandArgument as String;
                string fileName = Path.GetFileName(fileUrl);

                Response.AppendHeader("content-disposition",
        "attachment; filename=" + fileName);
                Response.ContentType = "application/zip";

                Response.WriteFile(fileUrl);
                Response.End();



            }
        }

private void BindData()
        {
            List<SampleFile> files = new List<SampleFile>();

            for(int i=1;i<=3;i++)
            {
                SampleFile sampleFile = new SampleFile();
                sampleFile.Name = "File " + i;
                sampleFile.Url = Server.MapPath("~/Files/File"+i+".txt");
                files.Add(sampleFile);
            }

            SampleFile file = new SampleFile();
            file.Name = "Zip File";
            file.Url = Server.MapPath("~/Files/WebSiteNestedMasters.zip");
            files.Add(file);
            gvFiles.DataSource = files;
            gvFiles.DataBind();
        }

<a href='<% Eval("Url")) %>'>download</a>

fileUrl = e.CommandArgument as String;
                string fileName = Path.GetFileName(fileUrl);

                FileStream fs = new FileStream(fileUrl, FileMode.Open);
                byte[] buffer = new byte[fs.Length];
                fs.Read(buffer, 0, (int) fs.Length);
                fs.Close();

                Response.Clear();
                Response.AppendHeader("content-disposition",
        "attachment; filename=" + fileName);
                Response.ContentType = "application/octet-stream";
                Response.AppendHeader("content-length", buffer.Length.ToString());

                Response.BinaryWrite(buffer);
                Response.Flush();
                Response.End();

if(e.CommandName.Equals("DownloadFile"))
            {
                fileUrl = e.CommandArgument as String;
                string fileName = Path.GetFileName(fileUrl);

                FileInfo info = new FileInfo(fileUrl);

                Response.Clear();
                Response.ClearContent();
                Response.ClearHeaders();
                Response.Buffer = true;

                Response.AppendHeader("Content-Length",info.Length.ToString());
                Response.ContentType = GetContentType(fileUrl);
                Response.AppendHeader("Content-Disposition:", "attachment; filename=" + fileName);
                Response.TransmitFile(fileUrl);
                Response.Flush();
                Response.End();
            }