Export GridView data to Excel in Asp.Net 2nd Method

protected void imgBtnExcel_Click(object sender, ImageClickEventArgs e)
{

    string attachment = "attachment; filename=Details.xls";
    Response.ClearContent();
    Response.AddHeader("content-disposition", attachment);
    Response.ContentType = "application/vnd.ms-excel";
    string tab = "";
    DataTable dtExcel = new DataTable();
    dtExcel = Session["ForExcelExport"] as DataTable;// Store The Data to Export
    foreach (DataColumn dc in dtExcel.Columns)
    {
        Response.Write(tab + dc.ColumnName);
        tab = "\t";
    }
    Response.Write("\n");
    int i;
    foreach (DataRow dr in dtExcel.Rows)
    {
        tab = "";
        for (i = 0; i < dtExcel.Columns.Count; i++)
        {
            Response.Write(tab + dr[i].ToString());
            tab = "\t";
        }
        Response.Write("\n");
    }
    Response.End();
}
public override void VerifyRenderingInServerForm(Control control)
{

}