Opret Excel fil i Memory og få data via DataSet

Jeg har fundet en masse eksmepler som  dette, men det giver mig vel ikke en Excel fil, men får bar Excel til at vise resultatet... eller?

using System;
using System.Data;
using System.IO;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace Whatever
{
///
/// This class provides a method to write a dataset to the HttpResponse as
/// an excel file.
///
public class ExcelExport
{
  public static void ExportDataSetToExcel(DataSet ds, string filename)
  {
  HttpResponse response = HttpContext.Current.Response;
 
  // first let's clean up the response.object
  response.Clear();
  response.Charset = "";
 
  // set the response mime type for excel
  response.ContentType = "application/vnd.ms-excel";
  response.AddHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");
 
  // create a string writer
  using (StringWriter sw = new StringWriter())
  {
    using (HtmlTextWriter htw = new HtmlTextWriter(sw))
    {
    // instantiate a datagrid
    DataGrid dg = new DataGrid();
    dg.DataSource = ds.Tables[0];
    dg.DataBind();
    dg.RenderControl(htw);
    response.Write(sw.ToString());
    response.End();
    }
  }
  }
}
}

lukker.