title: Expectation Failed when trying to update twitter status
body: <p>I can't seem to figure this one out. No matter what I do, I keep getting a "417 Expectation failed" error. Everywhere I've looked says that I need to get rid of the Expect header for the HttpWebRequest. Setting the static property <code>ServicePointManager.Expect100Continue = false</code> or the instance property on the web request <code>request.ServicePoint.Expect100Continue = false</code> never get's rid of the header. I have to manually set it to null to remove it.</p>
  
  <p>No matter what though, I STILL get the 417 error. What am I missing?</p>
  
  <pre><code>private static readonly MessageReceivingEndpoint UpdateStatusEndpoint 
         = new MessageReceivingEndpoint("http://twitter.com/statuses/update.xml", HttpDeliveryMethods.PostRequest);
  
  public static XDocument UpdateStatus(ConsumerBase twitter, string accessToken, string message)
  {
      var data = new Dictionary&lt;string, string&gt;();
      data.Add("status", message);
      ServicePointManager.Expect100Continue = false; //Doesn't work
      HttpWebRequest request = twitter.PrepareAuthorizedRequest(UpdateStatusEndpoint, accessToken, data);
  
      request.ServicePoint.Expect100Continue = false; //setting here doesn't work either
  
      //request.Expect is still set at this point unless I explicitly set it to null.
  
      request.Expect = null;
      var response = twitter.Channel.WebRequestHandler.GetResponse(request); //Throws exception
      return XDocument.Load(XmlReader.Create(response.GetResponseReader()));
  }
  </code></pre>