Project Structure

Learning objectives#

• Name the folders of an MVC 5 project and what goes in each
• Explain what Global.asax and App_Start do at startup
• Know the role of the two Web.config files
• Find where packages and bundles are configured

Explanation#

Controllers holds the controller classes; Models holds domain classes and view models; Views holds one subfolder per controller plus Shared for layouts, partials and the Error page.

App_Start contains small static classes that configure the app: RouteConfig (URLs), FilterConfig (global filters), BundleConfig (CSS/JS bundles) and, with Web API or Identity, WebApiConfig and Startup.Auth.

Global.asax.cs is the application class. Its Application_Start method runs once when IIS starts the app and calls the App_Start classes. It can also handle Application_Error and session events.

The root Web.config holds connection strings, app settings, authentication, compilation and assembly binding redirects. A second Web.config inside Views configures Razor and blocks direct requests to .cshtml files.

Content holds CSS and images, Scripts holds JavaScript (jQuery, validation), fonts holds web fonts, and packages.config lists NuGet packages. bin holds the compiled DLLs that IIS loads.

Syntax#

1ShopSite/
2├── App_Start/       BundleConfig.cs  FilterConfig.cs  RouteConfig.cs
3├── Content/         Site.css  bootstrap.css
4├── Controllers/     HomeController.cs  ProductsController.cs
5├── Models/          Product.cs  ProductViewModel.cs
6├── Scripts/         jquery-3.7.1.js  jquery.validate.js
7├── Views/
8│   ├── Home/        Index.cshtml
9│   ├── Products/    Index.cshtml  Details.cshtml
10│   ├── Shared/      _Layout.cshtml  Error.cshtml
11│   ├── _ViewStart.cshtml
12│   └── Web.config   (Razor settings)
13├── Global.asax(.cs)
14├── packages.config
15└── Web.config

Code example: What happens at startup#

1// Global.asax.cs
2using System;
3using System.Web;
4using System.Web.Mvc;
5using System.Web.Routing;
6

7namespace ShopSite
8{
9    public class MvcApplication : HttpApplication
10    {
11        // Runs once, when IIS starts (or recycles) the application
12        protected void Application_Start()
13        {
14            AreaRegistration.RegisterAllAreas();
15            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
16            RouteConfig.RegisterRoutes(RouteTable.Routes);
17            Application["StartedAt"] = "application started";
18        }
19    }
20}
21

22// Controllers/HomeController.cs
23using System.Web.Mvc;
24

25namespace ShopSite.Controllers
26{
27    public class HomeController : Controller
28    {
29        public ActionResult Index()
30        {
31            ViewBag.Title = "Home";
32            ViewBag.Started = HttpContext.Application["StartedAt"];
33            ViewBag.Routes = System.Web.Routing.RouteTable.Routes.Count;
34            ViewBag.Filters = GlobalFilters.Filters.Count;
35            return View();
36        }
37    }
38}
39

40@* Views/Home/Index.cshtml *@
41<p>Startup: @ViewBag.Started</p>
42<p>Routes registered: @ViewBag.Routes</p>
43<p>Global filters: @ViewBag.Filters</p>

GET /
200 OK
<p>Startup: application started</p>
<p>Routes registered: 2</p>
<p>Global filters: 1</p>

This example is illustrative. Copy or download it and run it in your own environment; the expected output is shown above.

Step-by-step explanation#

1. IIS loads the DLLs from bin and creates the MvcApplication class named in Global.asax.
2. Application_Start registers areas, global filters (HandleErrorAttribute) and routes.
3. The route table now holds 2 routes: the ignore rule for .axd files and the Default route. MapMvcAttributeRoutes adds entries only for controllers that use [Route].
4. Each request then uses that configuration; Application_Start does not run again until the app pool recycles.

Real-world use case#

Common mistakes#

Best practices#

• Keep App_Start classes small and focused
• Group views by controller and share layouts and partials in Views/Shared
• Put view models in a ViewModels folder once Models grows
• Use Web.Release.config transforms for production settings

Remember this#

Practice exercise#

1// App_Start/BundleConfig.cs
2using System.Web.Optimization;
3

4namespace ShopSite
5{
6    public class BundleConfig
7    {
8        public static void RegisterBundles(BundleCollection bundles)
9        {
10            bundles.Add(new StyleBundle("~/Content/css").Include("~/Content/site.css"));
11            bundles.Add(new ScriptBundle("~/bundles/jquery").Include("~/Scripts/jquery-{version}.js"));
12        }
13    }
14}
15

16// Global.asax.cs
17using System.Web;
18using System.Web.Mvc;
19using System.Web.Optimization;
20using System.Web.Routing;
21

22namespace ShopSite
23{
24    public class MvcApplication : HttpApplication
25    {
26        protected void Application_Start()
27        {
28            AreaRegistration.RegisterAllAreas();
29            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
30            RouteConfig.RegisterRoutes(RouteTable.Routes);
31            BundleConfig.RegisterBundles(BundleTable.Bundles);
32        }
33    }
34}

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