Export Gridview to Excel gridline not showing after download attached excel file

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C#

ASP.NET

Hello

I am using a code for download attached excel file.
After download this excel file Gridline of excel is automatically false.
Means Excel gridline not showing.

my code:-

Response.Clear();
            System.IO.StringWriter tw = new System.IO.StringWriter();
            HtmlTextWriter hw = new HtmlTextWriter(tw);
            
            Response.ContentType = "application/msexcel";
            //Response.AddHeader("Content-disposition", "attachment;filename=MyFiles.xls");
            Response.AddHeader("Content-disposition", string.Format("attachment;filename=MyFiles.xls; Gridlines=true"));
            

            using (StringWriter sw = new StringWriter())
            {
                using (HtmlTextWriter htw = new HtmlTextWriter(sw))
                {
                    Table table = new Table();

                    //  include the gridline settings
                    table.GridLines = gv.GridLines;

                    //  add the header row to the table
                    if (gv.HeaderRow != null)
                    {
                        table.Rows.Add(gv.HeaderRow);
                    }
                    foreach (GridViewRow row in gv.Rows)
                    {
                        table.Rows.Add(row);
                    }
                    table.RenderControl(htw);                   
                    HttpContext.Current.Response.Write(sw.ToString());
                    HttpContext.Current.Response.End();
                }
            }

please help