title: Knockout and ko.utils.postJson issue
body: <p>I was using some old example for MVC2, that used a [fromJson] attribute when posting json to a controller action, it worked fine except that it did not catch model errors, so ModelState.IsValid is always true. Then I saw that posting JSON was build into MVC3 so I have upgraded my code. But now I have another issue :) using:</p>
  
  <pre><code>ko.utils.postJson(location.href, json); 
  </code></pre>
  
  <p>The binding is not working, and my model is empty.</p>
  
  <p>But if I use JQuery:</p>
  
  <pre><code>$.ajax({
                              url: '@Url.Action("Create")',
                              contentType: 'application/json; charset=utf-8',
                              type: "POST",
                              data: json,
                              dataType: 'json',
                              success: function(result) {
                                  alert("yay");
                              },
                              error: function(xhr, ajaxOptions, thrownError) {
                                  alert(xhr.statusText + " " + xhr.responseText);
                              }
                          });
  </code></pre>
  
  <p>So I think i will move my ko.utils.postJson to JQuery $.ajax but how do I just post so I can do a RedirectToAction afterwards? </p>
  
  <p>So to clarify! the controller action looks like this:</p>
  
  <pre><code>public ActionResult Create(QuestionViewModel questionViewModel){
  
      if (ModelState.IsValid)
      {
          questionViewModel.Save();
  
          TempData.Add(Config.MODEL, questionViewModel);
          return RedirectToAction("Edit");
      }
  
      PopulateViewBag();
  
      return View(questionViewModel);
  }
  </code></pre>
  
  <p>I have found this <a href="http://groups.google.com/group/knockoutjs/browse_thread/thread/e631a544de2ad51e" rel="nofollow">http://groups.google.com/group/knockoutjs/browse_thread/thread/e631a544de2ad51e</a> in the Knockout forum so ko.utils.postJson is a "normal" form submit. which is what I want to do, so the flow of the application is kept unchanged.</p>