How Add new Row in Excel when we export gridview to excel pllz help me

Follow the below steps
1. Render GridView control to HTMLTextWriter
2. Copy TextWriter content to a StringBuilder variable
3. Prepare a html table row (<table><tbody><tr></tr></tbody></table>) with the values for the new row. Each column value should be within separate <table><tbody><tr><td></td></tr></tbody></table>
4. Using StringBuilder variable, insert the above row to the html just before end table tag ()
5. Now write the content using Response.Write()
6. This will download an excel with your new row

Response.Clear();
Response.AddHeader("content-disposition", "attachment;filename=Test.xls");
Response.Charset = "";
Response.ContentType = "application/vnd.xls";
StringWriter stringWrite = new StringWriter();
HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);

GridView1.RenderControl(htmlWrite);


StringBuilder sb = new StringBuilder(stringWrite.ToString());
sb = sb.Replace("</table>", "<tr><td>Column1</td><td>Column2</td></tr></table>");

Response.Write(sb);
Response.End();