Declaration of model in Razor View in mvc4 asp.net

Question

I am new to asp.net mvc4 and there is something i don't understand well.

Why do I have to declare the Model using @model at top of the view, if I already pass an object to the View in the controller.

Taking an example :

Controller:

public ActionResult countryDetails(int id)
    {

        Country country = db.Country.Find(id);
        return View(country);

    }

View:

@model MvcApplication2.Models.Country
@{
    ViewBag.Title = "countryDetails";
}
...

The controller returns a View with an object as parameter, so the model should be already known. I'm sorry if it is obvious, but I can't figure out why this is not a "double" declaration.

Thanks for you help !

Answer 1

The declaration at the top will do two things for you:

• It will allow intellisence to know what type you are using when you type in @Model or use any of the Html helper extensions.

• It will also check at runtime that model passed in can be cast to the type the view expects.

Its not necessarily a "double declaration" as it is analogous to specifying a type to a parameter on a method. Like so

Person Someone = new Person();
RenderView(Someone);
...
void RenderView(Person model) { }

Answer 2

By default your view inherits from System.Web.Mvc.WebViewPage<TModel>

You can optionally override this class, it's default ASP.NET inheritance mechanism:

@inherits System.Web.Mvc.WebViewPage<List<CompanyName.MyProduct.MyCategory>>

Or you can just simplify this since MVC3 like this:

@model List<CompanyName.MyProduct.MyCategory>

This sugar syntax was made to simplify code typing. This declaration give you some things

1. View automatically cast object to the preferred type
2. You receive type-defined 'model' property which allows you to access to your object methods and properties

Just believe that this is a method which accepts object and cast it to the specified type that you provide