Question

I´m still learning my way around MVC programming and have one question for you to clarify one thing for me regarding Get and POST ActionResult functions within my controllers. I´ll give you three possible scenarios (and actually three questions):

My first scenario:

public ActionResult Derp()
{
    Derpina derpina = new Derpina(); //Should I need to pass this to View?
    return View(derpina);
}

[HttpPost]
public ActionResult Derp()
{
    Derpina derpina = new Derpina();
    UpdateModel(derpina);
    //doStuff and save to DB
    return RedirectToAction("Index");
}

My second scenario:

public ActionResult Derp()
{
    return View();
}

[HttpPost]
public ActionResult Derp()
{
    Derpina derpina = new Derpina(); //Is this the cleanest way?
    UpdateModel(derpina);
    //doStuff and save to DB
    return RedirectToAction("Index");
}

My third scenario:

public ActionResult Derp()
{
    Derpina derpina = new Derpina();
    return View(derpina);
}

[HttpPost]
public ActionResult Derp(Derpina derpina)
{
    UpdateModel(derpina); //Should I need to do that at all?
    //doStuff and save to DB
    return RedirectToAction("Index");
}

I´m leaning toward the second scenario because I have no need to create new entity and pass it to the View. I guess that´s why I´m asking you guys, somebody told me once that there are no “stupid questions” so I hope you will bear with me 🙂

1. Should I need to pass newly created Derpina to the View
2. Isn´t the second scenario the “best practise”?
3. In the third scenario, if I pass Derpina as parameter into the HttpPost function, has the MVC framework not already updated the model?

Englis is not my native language so I hope these questions make any sense. Anyway, thank you in advance for any help you can give me to clarify.

EDITED

After one answer I received I want to add the fourth scenario:

public ActionResult CreateDerp()
{
    return View();
}

[HttpPost]
public ActionResult CreateDerp(Derpina derpina)
{
    UpdateModel(derpina);
    //doStuff and save to DB
    return RedirectToAction("Index");
}

Would that be the right approach, I mean if I´m not needed to send model to the View in the GET function? For instance if I were using Create functions like the above code suggests.

Answer 1

1st question -> If you have a view that must display data from your database, you need to send a model to the view so it can display the desired data on your page.

2nd question -> At post it is always recomended if not needed to get your model as a parameter in the post method, that`s the entire purpose of the model binder, how you update your data in the database should be separated in a bussines layer of your application, thats the cleanest way, in my opinion.

3rd question -> The mvc framework indeed created a new model containing the data from your view (if the user entered any), however, that does not mean it will update your object automatically or apply the changes in your database, you must do that explicitly, the way you require it.

I hope i’ve been at least a bit helpful.