title: How to force WebRequest to send Authorization header during POST
body: <p>When using WebRequest to send a POST, the Authorization header is not sent with the request even though I have manually set the header and set PreAuthenticate to true, eg:</p>
  
  <pre><code>webRequest.Headers["Authorization"] = "OAuth oauth_consumer_key=bFPD...";
  webRequest.PreAuthenticate = true;
  </code></pre>
  
  <p>Using Fiddler I can see that the Authorization header is not sent. The target site (Twitter) returns a 400 (Bad request) rather than a 401 (Not authorized) which is therefore the incorrect challenge required for WebRequest to send the Authorization data. For information, the returned content is:</p>
  
  <pre><code>{"errors":[{"message":"Bad Authentication data","code":215}]}
  </code></pre>
  
  <p>So, how do I get around this? How can I force WebRequest to send the Authorization with initial request? Note that the authorization data is not Basic Authentication, rather it is an OAuth string.</p>
  
  <p>Thanks</p>