Chapter 2: Your First ASP.NET MVC Application

This chapter describes the ASP.NET MVC project template that is installed in Visual Studio. A simple application is built, briefly touching on all of the aspects of the ASP.NET MVC framework.

What's inside the box?

After the ASP.NET MVC project has been created, you will notice a default folder structure. There's a Controllers folder, a Models folder, a Views folder, as well as a Content folder and a Scripts folder. ASP.NET MVC comes with the convention that these folders (and namespaces) are used for locating the different blocks used for building the ASP.NET MVC framework. The Controllers folder obviously contains all of the controller classes; the Models folder contains the model classes; while the Views folder contains the view pages. Content will typically contain web site content such as images and stylesheet files, and Scripts will contain all of the JavaScript files used by the web application. By default, the Scripts folder contains some JavaScript files required for the use of Microsoft AJAX or jQuery.

Locating the different building blocks is done in the request life cycle, which is described in Chapter 4, Components in the ASP.NET MVC Framework. One of the first steps in the ASP.NET MVC request life cycle is mapping the requested URL to the correct controller action method. This process is referred to as routing. A default route is initialized in the Global.asax file and describes to the ASP.NET MVC framework how to handle a request. Double-clicking on the Global.asax file in the MvcApplication1 project will display the following code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
namespace MvcApplication1
{
    public class GlobalApplication : System.Web.HttpApplication
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
            routes.MapRoute(
                "Default",// Route name
                "{controller}/{action}/{id}",// URL with parameters
                new { controller = "Home", action = "Index",id = "" } // Parameter defaults
                );
        }
        protected void Application_Start()
        {
            RegisterRoutes(RouteTable.Routes);
        }
    }
}

In the Application_Start() event handler, which is fired whenever the application is compiled or the web server is restarted, a route table is registered. The default route is named Default, and responds to a URL in the form of http://www.example.com/{controller}/{action}/{id}. The variables between { and } are populated with actual values from the request URL or with the default values if no override is present in the URL. This default route will map to the Home controller and to the Index action method, according to the default routing parameters. We won't have any other action with this routing map.

By default, all possible URLs can be mapped through this default route. It is also possible to create our own routes. For example, let's map the URL http://www.example.com/Employee/Maarten to the Employee controller, the Show action, and the firstname parameter. The following code snippet can be inserted in the Global.asax file we've just opened. Because the ASP.NET MVC framework uses the first matching route, this code snippet should be inserted above the default route; otherwise the route will never be used.

routes.MapRoute(
    "EmployeeShow", // Route name
    "Employee/{firstname}", // URL with parameters
    new
    { // Parameter defaults
        controller = "Employee",
        action = "Show",
        firstname = ""
    }
    );