Modern way to handle and validate POST-data in MVC 2

Question

There are a lot of articles devoted to working with data in MVC, and nothing about MVC 2.

So my question is: what is the proper way to handle POST-query and validate it.

Assume we have 2 actions. Both of them operates over the same entity, but each action has its own separated set of object properties that should be bound in automatic manner. For example:

• Action "A" should bind only "Name" property of object, taken from POST-request
• Action "B" should bind only "Date" property of object, taken from POST-request

As far as I understand - we cannot use Bind attribute in this case.

So - what are the best practices in MVC2 to handle POST-data and probably validate it?

UPD:
After Actions performed - additional logic will be applied to the objects so they become valid and ready to store in persistent layer. For action "A" - it will be setting up Date to current date.

Answer 1

I personally don't like using domain model classes as my view model. I find it causes problems with validation, formatting, and generally feels wrong. In fact, I'd not actually use a DateTime property on my view model at all (I'd format it as a string in my controller).

I would use two seperate view models, each with validation attributes, exposed as properties of your primary view model:

NOTE: I've left how to combining posted view-models with the main view model as an exercise for you, since there's several ways of approaching it

public class ActionAViewModel
{
    [Required(ErrorMessage="Please enter your name")]
    public string Name { get; set; }
}

public class ActionBViewModel
{
    [Required(ErrorMessage="Please enter your date")]
    // You could use a regex or custom attribute to do date validation,
    // allowing you to have a custom error message for badly formatted
    // dates
    public string Date { get; set; }
}

public class PageViewModel
{
    public ActionAViewModel ActionA { get; set; }
    public ActionBViewModel ActionB { get; set; }
}

public class PageController
{
    public ActionResult Index()
    {
        var viewModel = new PageViewModel
        {
            ActionA = new ActionAViewModel { Name = "Test" }
            ActionB = new ActionBViewModel { Date = DateTime.Today.ToString(); }
        };

        return View(viewModel);
    }

    // The [Bind] prefix is there for when you use 
    // <%= Html.TextBoxFor(x => x.ActionA.Name) %>
    public ActionResult ActionA(
        [Bind(Prefix="ActionA")] ActionAViewModel viewModel)
    {
        if (ModelState.IsValid)
        {
            // Load model, update the Name, and commit the change
        }
        else
        {
            // Display Index with viewModel
            // and default ActionBViewModel
        }
    }

    public ActionResult ActionB(
        [Bind(Prefix="ActionB")] ActionBViewModel viewModel)
    {
        if (ModelState.IsValid)
        {
            // Load model, update the Date, and commit the change
        }
        else
        {
            // Display Index with viewModel
            // and default ActionAViewModel
        }
    }
}

Answer 2

One possible way to handle POST data and add validation, is with a custom model binder. Here is a small sample of what i used recently to add custom validation to POST-form data :

public class Customer
{
    public string Name { get; set; }
    public DateTime Date { get; set; }
}


public class PageController : Controller
{
    [HttpPost]
    public ActionResult ActionA(Customer customer)
    {
        if(ModelState.IsValid) {
        //do something with the customer
        }
    }

    [HttpPost]
    public ActionResult ActionB(Customer customer)
    {
       if(ModelState.IsValid) { 
       //do something with the customer
       }
    }
}

A CustomerModelBinder will be something like that:

    public class CustomerModelBinder : DefaultModelBinder
{
    protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor)
    {
        if (propertyDescriptor.Name == "Name") //or date or whatever else you want
        {


            //Access your Name property with valueprovider and do some magic before you bind it to the model.
            //To add validation errors do (simple stuff)
            if(string.IsNullOrEmpty(bindingContext.ValueProvider.GetValue("Name").AttemptedValue))
                bindingContext.ModelState.AddModelError("Name", "Please enter a valid name");

            //Any complex validation
        }
        else
        {
            //call the usual binder otherwise. I noticed that in this way you can use DataAnnotations as well.
            base.BindProperty(controllerContext, bindingContext, propertyDescriptor); 
        }
    }

and in the global.asax put

ModelBinders.Binders.Add(typeof(Customer), new CustomerModelBinder());

If you want not to bind Name property (just Date) when you call ActionB, then just make one more custom Model Binder and in the "if" statement, put to return the null, or the already existing value, or whatever you want. Then in the controller put:

[HttpPost]
public ActionResult([ModelBinder(typeof(CustomerAModelBinder))] Customer customer)

[HttpPost]
public ActionResult([ModelBinder(typeof(CustomerBModelBinder))] Customer customer)

Where customerAmodelbinder will bind only name and customerBmodelbinder will bind only date.

This is the easiest way i have found, to validate model binding, and i have achieved some very cool results with complex view models. I bet there is something out there that i have missed, and maybe a more expert can answer. Hope i got your question right...:)