title: MVC 3 model value lost on 2nd post back
body: <p>I have a view with a model that has several fields.  When I render the view on the GET I have a hidden field storing a code which is empty at this point.  Then I POST and on the action I add a value to this code field through the model and send the model to the view like:</p>
  
  <pre><code>return View (model);
  </code></pre>
  
  <p>When the view renders, the hidden field does not have the code value but the view does contain all other values entered in the first step. So now when I post on a second button the model passed to the action does not contain the hidden code value I passed to it on the first post response.</p>
  
  <p>If I updated the model on the first post sent it back to the view with new values, should I not get that code stored in a hidden input in the view available and being able to post it back again to the action? </p>
  
  <p>I just also realized that if I change any model field on the first post back and send the updated model to the view it will only retain values from the first POST action. Do I have a cache issue here?, how do i manage this behavior? thanks</p>