Understanding MVC4 Controllers

Question

I'm fairly new to the .net Framework and the whole MVC programming philosophy. Could someone clarify and give me a basic explanation how controllers interact with sites using C#? I understand how to code in C#, and I understanding some aspects of the framework, but I don't see how they all tie together.

Answer 1

Model - Is a data structure that represents some kind of object (usually one). It's purpose is to read, write and manage the access to the underlying object with the aim to persist application state.

View - Is the components that are used to display a visual interface to the user, perhaps using a model. It might be a simple table or a complex combination into a full web page.

Controller - Is the user driven application logic layer the sits between views and models. It handlers user interaction, loads models, and sends views to the user. It determines what model is sent to the view depending on user requests.

The overall folder structure for an application might look like this.

>> Website
     >> Controllers
     >> Models
     >> Views

In C# MVC each controller must have the suffix Controller in the name, they must extend Controller class and have a folder of the name prefix (without the Controller) in the views folder. This folder will then contain all the views related to particular actions on the controller.

Controllers can contain any number of actions defined as public functions. By default when returning a result from a controller action the name of the view must correspond with the name of the action. However you can also specify a view by name. When loading a view from a controller, it is possible to send an object as a model to the view and there by generate it's content.

Controllers can load any model and are not restricted in any way.

An Account controller defined as below with an action Login. The controller is placed in a AccountController.cs file in the /Controllers folder, and any views for this controller (Login in this instance with filename Login.cshtml) are placed in the /Views/Account folder.

Note: The naming convention has to be right as the names are used between the controllers and views to link the data.

public class AccountController : Controller
{
    public ActionResult Login(string returnUrl)
    {
        if (User.Identity.IsAuthenticated)
        {
            return RedirectToAction("Index","Site");
        }

        return View("Login", new LogOnModel());
    }
}

would be accessible via http://www.mysite.com/Account/Login. If the user is authenticated, the controller will redirect to the main site controller, if the user is not logged in then they are shown the Login view which loads data from the LogOnModel specified.

This is really just touching the surface of what is possible. Read some online information on some excellent articles by ScottGu which go into much more depth and talk you through how to use MVC.

ASP.NET MVC Framework Overview

ASP.NET MVC Framework How To - Part 1 // Part 2 // Part 3 // Part 4

Note : These articles are slightly outdated as they were written for MVC version 1 back in 2007, but the concepts of how the Models, Views and Controller interact still apply.