title: AD FS 2.0 Authentication and AJAX
body: <p>I have a web site that is trying to call an MVC controller action on another web site. These sites are both setup as relying party trusts in AD FS 2.0. Everything authenticates and works fine when opening pages in the browser window between the two sites. However, when trying to call a controller action from JavaScript using the jQuery AJAX method it always fails. Here is a code snippet of what I'm trying to do...</p>
  
  <pre><code>$.ajax({
    url: "relyingPartySite/Controller/Action",
    data: { foobar },
    dataType: "json",
    type: "POST",
    async: false,
    cache: false,
    success: function (data) {
      // do something here
    },
    error: function (data, status) {
      alert(status);
    }
  });
  </code></pre>
  
  <p>The issue is that AD FS uses JavaScript to post a hidden html form to the relying party. 
  When tracing with Fiddler I can see it get to the AD FS site and return this html form which should post and redirect to the controller action authenticated. The problem is this form is coming back as the result of the ajax request and obviously going to fail with a parser error since the ajax request expects json from the controller action. It seems like this would be a common scenario, so what is the proper way to communicate with AD FS from AJAX and handle this redirection?</p>