Execute code after CompleteRequest()

I have to execute some more code after downloading a file, but itsn't happening. The compiler hits `ClearControls();` after `DownloadFile();`, but the function is not executed.
On the page I get the prompt to open or save the file. But the textboxes are not cleared.
What should be done in this case.

protected void btnOk_Click(object sender, EventArgs e)
    {
    //ClearControls(); // not working here too.
    DownloadFile();
    ClearControls();
    }

    private void DownloadFile()
    {
    Response.ContentType = "application/pdf";
    Response.AppendHeader("Content-Disposition","attachment;filename="+sName+".pdf");
    Response.TransmitFile(Server.MapPath("~/documents/ready/" + strPdfName));
    //Response.End();
    HttpContext.Current.ApplicationInstance.CompleteRequest();
    }

    private void ClearControls()
    {
      txtOne.Text="";
      txtTwo.Text="";
    }