The use of App_Start() folder in MVC4

App_start folder has been introduced in Mvc4. It contains various configurations files like as :

• BundleConnfig.cs,
• FilterConfig.cs,
• RouteConfig.cs,
• WebApiConfig.cs

for you application.All those settings are registered within App_Start method of Global.asax.cs file

BundleConfig.cs:

This is used to create and register bundles for CS and JS files.By default various bundles are added in this file including jQuery,jQueryUI,jQuery validation,Modernizr and Site Css..

FilterConfig.cs-

This is used to create and register global MVC filter error filter,action filter etc.By default it contains HandleErrorAttribute filter.

RouteConfig.cs-

This is used to register various route patterns for your Asp.Net MVC application. By default,one route is registered here named as Default Route.

WebApiConfig.cs-

This is used to register various WEB API routes like as Asp.Net MVC,as well sa set any addtionsl WEB ApI configurations settings.

• AuthConfi g.cs: Used to confi gure security settings, including sites for OAuth login.
• BundleConfi g.cs: Used to register bundles used by the bundling and minifi cation system. Several bundles are added by default, including jQuery, jQueryUI, jQuery validation, Modernizr, and default CSS references.
• FilterConfi g.cs: Unsurprisingly, this is used to register global MVC fi lters. The only fi lter registered by default is the HandleErrorAttribute, but this is a great place to put other fi lter registrations.
• RouteConfi g.cs: Holds the granddaddy of the MVC confi g statements, Route confi guration.
• WebApiConfi g.cs: Used to register Web API routes, as well as set any additional Web API confi guration settings.
• public class MvcApplication : System.Web.HttpApplication
  {
    protected void Application_Start()
    {
      AreaRegistration.RegisterAllAreas();
      WebApiConfig.Register(GlobalConfiguration.Configuration);
      FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
      RouteConfig.RegisterRoutes(RouteTable.Routes);
    }
  }
• It does 4 tasks:

  • Register areas
  • Register Web Api configuration
  • Register global filters
  • Register routes

  So, where are the initialization code now?

  The template creates the “App_Start” folder and adds 3 class files:

  • FilterConfig.cs
  • RouteConfig.cs
  • WebApiConfig.cs

  The initialization code is defined in the static method of each class.

  
  

  4. Routes Initialization in MVC 4

  The “RouteConfig” class defines the static “RegisterRoutes()” method.

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  public class RouteConfig {   public static void RegisterRoutes(RouteCollection routes)   {     routes.IgnoreRoute("{resource}.axd/{*pathInfo}");       routes.MapRoute(       name: "Default",       url: "{controller}/{action}/{id}",       defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }     );   } }

  By using the named arguments, the code becomes more readable.
   

  5. Global Filters in MVC 4

  The “FilterConfig” class defines the static “RegisterGlobalFilters()” method.

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  public class FilterConfig {   public static void RegisterGlobalFilters(GlobalFilterCollection filters)   {     filters.Add(new HandleErrorAttribute());   } }

  
  

  6. Web API Configuration in MVC 4

  The “Web API” is a nice addition to ASP.NET and is available from MVC 4.

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  public static class WebApiConfig {   public static void Register(HttpConfiguration config)   {     config.Routes.MapHttpRoute(       name: "DefaultApi",       routeTemplate: "api/{controller}/{id}",       defaults: new { id = RouteParameter.Optional }     );   } }