Send ViewModel back to controller with POST

Question

For MVC4, What's the best-practice way to send a ViewModel used to populate a view back to a controller via POST?

Answer 1

Lets assume you want a login form with this view model:

public class LoginModel
{
    [Required]
    public string UserName { get; set; }

    [Required]
    [DataType(DataType.Password)]
    public string Password { get; set; }

    public bool RememberMe { get; set; }
}

Using this view model in a view is straight-forward, just send a new instance of LoginModel to the view:

public ActionResult Login()
{
    var model = new LoginModel();
    return View(model);
}

Now we can create the Login.cshtml view:

@model App.Models.LoginModel

@using (Html.BeginForm())
{
    @Html.LabelFor(model => model.UserName)
    @Html.TextBoxFor(model => model.UserName)
    @Html.ValidationMessageFor(model => model.UserName)

    @Html.LabelFor(model => model.Password)
    @Html.PasswordFor(model => model.Password)
    @Html.ValidationMessageFor(model => model.Password)

    @Html.CheckboxFor(model => model.RememberMe)
    @Html.LabelFor(model => model.RememberMe)

    <input type="submit" value="Login" />
}

Now we have to create an action in the controller which handles the post of this form. We can do that like this:

[HttpPost]
public ActionResult Login(LoginModel model)
{
    if (ModelState.IsValid)
    {
        // Authenticate the user with information in LoginModel.
    }

    // Something went wrong, redisplay view with the model.
    return View(model);
}

The HttpPost attribute will ensure that the controller action only can be reached via a post request.

MVC will use its magic and binds all the properties from the view back to a LoginModel instance populated with the values from the post.

Answer 2

One way is to have your Post controller accept the ViewModel as its parameter then map its properties to your domain model.

public class Model
{
     public DateTime Birthday {get;set;}
}

public class ViewModel
{
     public string Month {get;set;}
     public string Day {get;set;}
     public string Year {get;set;}
}

Controller

[HttpPost]
public ActionResult Create(ViewModel viewModel)
{
    string birthday = viewModel.Month + "/" + viewModel.day + "/" + viewModel.year;

    Model model = new Model { Birthday = Convert.ToDateTime(birthday) } ;
    // save 
    return RedirectToAction("Index");
}