把DataGrid导出到excel

btnExport is a BUTTON Control; DataGrid1 is a DataGrid Control

private void btnExportExcel_Click(object sender, System.EventArgs e) 

{

            HttpContext.Current.Response.Charset ="UTF-8";
            HttpContext.Current.Response.ContentEncoding =System.Text.Encoding.Default;
            HttpContext.Current.Response.ContentType ="application/ms-excel";
            DataGrid1.Page.EnableViewState =false;

            System.IO.StringWriter  sw = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(sw);
            DataGrid1.RenderControl(hw);
            HttpContext.Current.Response.Write(sw.ToString());
            HttpContext.Current.Response.End();

}

 导出到Excel,数字内容显示不正确

private void dgShow_ItemCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
  {
         if(e.Item.ItemType  ==  ListItemType.Item  ||  e.Item.ItemType  ==  ListItemType.AlternatingItem)
         {
                e.Item.Cells[4].Attributes.Add("style","vnd.ms-excel.numberformat:@");

                .......
         }

  }