title: Model binder does not convert json to IEnumerable<T>
body: <p>I am sending json data to my controller action via jquery ajax post. The IEnumerable in my action is alway null.</p>
  
  <p>Is my json wrong or why does the model binder not convert the json to the IEnumerable ?</p>
  
  <pre><code>public ActionResult Update(IEnumerable&lt;Teststep&gt; teststeps)
  {
     //
  }
  
  $.ajax({
              url: '@Url.Action("Update", "Teststep")',
              type: 'POST',
              data: [{ "errortext": "oh something bad happended.", "unitid": "10" }, { "errortext": "you got it man.", "unitid": "20"}],
              success: function (response) {
                  debugger;
                  if (response.success) {
                      dlg.dialog("close");
                      // Update UI
  
                  }
                  else {
                      // Reload the dialog with the form to show model/validation errors 
                      dlg.html(response);
                  }
              }
          });
  
  public class Teststep
  {
  
   [HiddenInput(DisplayValue = false)]
   public int UnitId { get; set; }    
  
   public string ErrorText { get; set; }  
  
   // some other props removed for readability   
  
  }
  </code></pre>