download file where URL generate file dynamically

private void button1_Click(object sender, EventArgs e)
 {
     WebRequest objReq = WebRequest.Create("http://www.martinfowler.com/ieeeSoftware/patterns.pdf");
     WebResponse objResp = objReq.GetResponse();
     Stream objStream = objResp.GetResponseStream();
     StreamReader reader = new StreamReader(objStream,Encoding.ASCII);
     FileStream fStream = new FileStream("Test.pdf", FileMode.Create);
     StreamWriter writer=new StreamWriter(fStream);
     writer.Write(reader.ReadToEnd());
     objStream.Close();
     reader.Close();
     writer.Close();
     fStream.Close();

 }