Question

I’m developing something like wizard with steps (controllers) and uses DerivedModel1, DerivedModel2,etc which is inherits from BaseModel and extends them with extra properties.
Models – only data, without business logic. All logic performed by services in controllers action for example _step1Service.GetRelated(model.id).

Now I want to not just validate Model (for this case there is ValidationAttribute) but fix invalid data in BaseModel:

 public class BaseModel
 {
     public DateTime StartDate {get;set;}
 }

StartDate should be greater than today. User can select invalid date and instead of validation error application should fix this value (reset to default?).

In my first attempt I added service for validating/correcting StartDate and call in each Action:

public ActionResult Index(DerivedModel1 model)
{
_svc.fixModel(model);

if(!ModelState.IsValid)
{
return View();
}

... do stuff with valid data
}

But don’t like that, because have to add this line to each controller and action.
Then I add this correction to StartDate setter. It’s looks better, but this breaks popular MVC paradigm that all logic should be in controller (or maybe i misunderstood something?)
I was thinking about possible solutions of this problem: ActionFilterAttribute, custom ModelBinder? But not sure is this right way and whether it work.
What you think about that?

Answer 1

you must implement IModelBinder to achieve this.

first define your custom model binder like this:

public class MyCustomModelBinder : IModelBinder
{
   public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            // Get the raw attempted value from the value provider
            DateTime incomingDate = (DateTime) bindingContext.ValueProvider.GetValue("datefield").AttemptedValue;
            //validate and correct date here ...
            return new BaseModel{ DateMember =  incomingDate };
        }
}

then register your custom model binder such:

protected void Application_Start()
{
       ModelBinders.Binders.Add(typeof (BaseModel), new MyCustomModelBinder());          
}

and your controller :

public ActionResult YourAction([ModelBinder(typeof(MyCustomModelBinder )] BaseModel model)
{
      return Content("Ok");
}