title: Stream and XmlTextwriter.... Request is not received correctly
body: <p>Im stuck on this httpWebRequest problem. I need to send XML to a website. But I keep getting negative responses on my request. I saw some code examples where the ContentLength was set... And that might be the issue but I don't know....</p>
  
  <p>The XML written in writePaymentRequest(...) is exactly as the website needs it to be, because they got my xml markup and they succeeded, in another programming language though. The result only contains their error instead of the information I'm supposed to be receiving.</p>
  
  <p>I can't set the contentlength because I don't know the length when I create the writer with the requeststream in it.</p>
  
  <pre><code>HttpWebRequest httpWebRequest = (HttpWebRequest)HttpWebRequest.Create("https://some.website.com");
  httpWebRequest.Method = "POST";
  httpWebRequest.ContentType = "application/x-www-form-urlencoded";
  
  using (writer = new XmlTextWriter(httpWebRequest.GetRequestStream(), System.Text.Encoding.UTF8))
  {
   writePaymentRequest(writer, registrant, amount, signature, ipaddress);
  }
  
  HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
  StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream());
  String stringResult = streamReader.ReadToEnd();
  streamReader.Close();
  </code></pre>