ASP.NET MVC - State and Architecture

Question

After a pair programming session, an interesting question came up which I think I know the answer for.

Question: Is there any other desired way in ASP.NET MVC to retain 'state' other than writing to database or a text file?

I'm going to define state here to mean that we have a collection of person objects, we create a new one, and go to another page, and expect to see the newly created person. (so no Ajax)

My thoughts are we don't want any kung-fu ViewState or other mechanisms, this framework is about going back to a stateless web.

Answer 1

What about user session? There are plenty of valid use cases to store things in session. And what about a distributed caching system like memcached? You also seem to leave out the query string - which is an excellent state saver (?page=2). To me those seem like other desirable methods to save state across requests...?

Answer 2

"My thoughts are we don't want any kung-fu ViewState or other mechanisms, this framework is about going back to a stateless web."

The example you provided is pretty easy to do without any sort of "view state kung fu" using capabilities that are already in MVC. "User adds a person and sees that on the next screen." Let me code up a simple PersonController that does exactly what you want:

    public ActionResult Add()
    {
        return View(new Person());
    }

    [HttpPost]
    public ActionResult Add(PeronViewModel myNewPersonViewModel )
    {
        //validate, user entered everything correctly
        if( !ModelState.IsValid ) x
            return View();

         //map model to my database/entity/domain object
         var myNewPerson = new Person()
                               {
                                     FirstName = myNewPersonViewModel.FirstName,
                                     LastName = myNewPersonViewModel.LastName
                               }

        //1. maintains person state, sends the user to the next view in the chain
        //using same action
        if( MyDataLayer.Save( myNewPerson ) )
        {
             var persons = MyDataLayer.GetPersons();
             persons.Add(myNewPersion);

             return View("PersonGrid",persons); 
        }

        //2. pass along the unique id of person to a different action or controller
        //yes, another database call, but probably not a big deal 
        if( MyDataLayer.Save( myNewPerson ) )
             return RedirecToAction("PersonGrid", ...etc pass the int as route value); 

        return View("PersonSaveError", myNewPersonViewModel);
    }

Now what I'm sensing is that you want person on yet another page after PersonSaveSuccess or something else. In that case you probably want to use TempData[""] which is a single serving session and only saves "state" from one request to another or manage the traditional Session[""] yourself somehow.

What is confusing to me is your probably going to the db to get all your persons anyway. If you save a person it should be in your persons collection in the next call to your GetPersons(). If your not using Ajax, than what state are you trying to persist?

Answer 3

ASP.NET MVC offers a cleaner way of working with session storage using model binding. You can write a custom model binder that can supply instances from session to your action methods. Look it up.