ASP.NET MVC and ViewState

Question

Now I've seen some questions like this, but it's not exactly what I want to ask, so for all those screaming duplicate, I apologize :).

I've barely touched ASP.NET MVC but from what I understand there is no ViewState/ControlState... fine. So my question is what is the alternative to retaining a control's state? Do we go back to old school ASP where we might simulate what ASP.NET ViewState/ControlState does by creating hidden form inputs with the control's state, or with MVC, do we just assume AJAX always and retain all state client-side and make AJAX calls to update?

This question has some answers, Maintaining viewstate in Asp.net mvc?, but not exactly what I'm looking for in an answer.

UPDATE: Thanks for all the answers so far. Just to clear up what I'm not looking for and what I'm looking for:

Not looking for:

• Session solution
• Cookie solution
• Not looking to mimic WebForms in MVC

What I am/was looking for:

• A method that only retains the state on postback if data is not rebound to a control. Think WebForms with the scenario of only binding a grid on the initial page load, i.e. only rebinding the data when necessary. As I mentioned, I'm not trying to mimic WebForms, just wondering what mechanisms MVC offers.

Answer 1

The answer really depends on the types of controls you are trying to maintain state for. For basic Html controls then it is very easy to maintain state with your Models, to do this you need to create a strongly typed view.

So if we had a User model with the properties: Username, FullName, Email, we can do the following in the view:

<%= Html.ValidationSummary() %>

<% using (Html.BeginForm()) { %>
  <fieldset>
    <legend>User details</legend>
    <%= Html.AntiForgeryToken() %>

    <p>
      <label for="Username">Username:</label>
      <%= Html.Textbox("Username", Model.Username, "*") %>
    </p>
    <p>
      <label for="FullName">FullName:</label>
      <%= Html.Textbox("FullName", Model.FullName, "*") %>
    </p>
    <p>
      <label for="Email">Email:</label>
      <%= Html.Textbox("Email", Model.Email, "*") %>
    </p>
    <p>
       <input type+"submit" value="Save user" />
    </p>
  </fieldset>
<% } %>

We would then have two controller actions that display this view, one for get and another for post:

[AcceptVerbs(HttpVerbs.Get)]
public ActionResult User()
{
  return View(new User())
}

[AcceptVerbs(HttpVerbs.Post)]
[ValidateAntiForgeryToken]
public ActionResult User([Bind(Include = "Username,FullName,Email")]User user)
{
   if (!ModelState.IsValid()) return View(user);

   try
   {
     user.save()
     // return the view again or redirect the user to another page
   }
   catch(Exception e)
   {
     ViewData["Message"] = e.Message;
     return View(user)
   }
}

Is this what you are looking for? Or do you want to maintain the state of Models that are not being displayed in a form between requests?

The key thing to remember is that your code executes on the server for the duration of the request and ends, the only information you can pass between your requests is basic html form data, url parameters and session information.

As other people have mentioned, I'd highly recommend Steve Sandersan's Pro ASP.NET MVC Framework for a complete understanding of working with the MVC Framework.