Response.Clear();
 Response.AddHeader("content-disposition", "attachment;filename=SalesPersonreport.xls");
 Response.Charset = "";   // If you want the option to open the Excel file without saving then  // comment out the line below  // 
            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            Response.ContentType = "application/vnd.xls";
            System.IO.StringWriter stringWrite = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);

            GridView gvExport = new GridView();// grid a grid typr instance for exporting grid data to excel
            if (dsReport.Tables[0].Rows.Count > 0)
            {
                gvExport.DataSource = dsReport;//objbus.ExporttoExcel(querryvalue); 
                gvExport.DataBind();
            }

            gvExport.RenderControl(htmlWrite); // rendering grid data to html writter
            Response.Write(stringWrite.ToString()); //this will prompt Download message