title: ASP.NET form losing POST values in a proxy environment
body: <p>I have an ASP.NET form (a login page), when I POST the values to the server, the request passes through a proxy and the POST pareameters end up getting lost and ultimately the page just refreshes as there are no POST parameters.</p>
  
  <p>The thing is that this is not a constant issue as sometimes you can log in fine and generally if you clear your browser temp files it then works ok.</p>
  
  <p>I ran Fiddler to check what's going on and basically I'm getting:</p>
  
  <ul>
  <li>A regular POST request containing session id, POST data etc. The response (HTTP 407) contains a Proxy-Authenticate: Negotiate and Proxy-Support: Session-Based-Authentication header</li>
  <li>The next request to the server contains a Proxy-Authorization: Negotiate header containing a long string (base64 i think). This request does NOT contain the POST values. The response is another 407 and actually now that i look at it Fiddler displays 'HTTP/1.1 407 Proxy Authentication Required ( Access is denied.  )' as the header.</li>
  <li>Then there's a third request that contains the Proxy-Authorization header and returns 200 OK, but of course the POST values weren't sent</li>
  </ul>
  
  <p>Subsequent requests result in a HTTP/1.1 407 Proxy Authentication Required ( The ISA Server requires authorization to fulfill the request. Access to the Web Proxy filter is denied.  ) response followed by a second successful but empty request.</p>
  
  <p>The client wont let me bypass the proxy as it's intermittent and all other pages in the application (that include plenty of web forms) work fine. </p>
  
  <p>Any ideas on what I can try?</p>