Asp.net MVC Request Life Cycle

Asp.net MVC Request Life Cycle: An Overview

In this MVC Tutorial, I am going to expose the Asp.net MVC Request Life cycle. While programming with Asp.net MVC, you should be aware of the life of an Asp.net MVC request from birth to death. To understand MVC concepts from the scratch, enroll in our ASP.NET MVC Certification Training right now!

Read More: MVC Interview Questions and Answers

The steps of ASP.NET MVC Request Life Cycle

There are seven main steps that happen when you make a request to an Asp.net MVC web application. For more details refer Detailed ASP.NET MVC Pipeline.

1. Routing

   Asp.net Routing is the first step in the MVC request cycle. Basically, it is a pattern-matching system that matches the request’s URL against the registered URL patterns in the Route Table. When a matching pattern is found in the Route Table, the Routing engine forwards the request to the corresponding IRouteHandler for that request. The default one calls the MvcHandler. The routing engine returns a 404 HTTP status code against that request if the patterns are not found in the Route Table.

   When an application starts for the first time, it registers one or more patterns to the Route Table to tell the routing system what to do with any requests that match these patterns. An application has only one Route Table and this is set up in the Global.asax file of the application.

   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 = UrlParameter.Optional } // Parameter defaults
    ); 
   } 

   Read More: A Brief History of ASP.NET MVC Framework



2. MvcHandler

   The MvcHandler is responsible for initiating the real processing inside ASP.NET MVC. MVC handler implements the IHttpHandler interface and further processes the request by using ProcessRequest method as shown below:

   protected internal virtual void ProcessRequest(HttpContextBase httpContext)
   {
    SecurityUtil.ProcessInApplicationTrust(delegate {
    IController controller;
    IControllerFactory factory;
    this.ProcessRequestInit(httpContext, out controller, out factory);
    try
    {
    controller.Execute(this.RequestContext);
    }
    finally
    {
    factory.ReleaseController(controller);
    }
    });
   }
   

3. Controller

   As shown in the above code, MvcHandler uses the IControllerFactory instance and tries to get an IController instance. If successful, the Execute method is called. The IControllerFactory could be the default controller factory or a custom factory initialized at the Application_Start event, as shown below:

   protected void Application_Start()
   {
    AreaRegistration.RegisterAllAreas();
    RegisterRoutes(RouteTable.Routes);
    ControllerBuilder.Current.SetControllerFactory(new CustomControllerFactory());
   }
   

4. Action Execution

   Once the controller has been instantiated, the Controller's ActionInvoker determines which specific action to invoke on the controller. Action to be executed is chosen based on attributes ActionNameSelectorAttribute (by default method which has the same name as the action is chosen) and ActionMethodSelectorAttribute(If more than one method is found, the correct one is chosen with the help of this attribute).

5. View Result

   The action method receives user input, prepares the appropriate response data, and then executes the result by returning a result type. The result types can be ViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult, and EmptyResult.

6. View Engine

   The first step in the execution of the View Result involves the selection of the appropriate View Engine to render the View Result. It is handled by IViewEnginean interface of the view engine. By default Asp.Net MVC uses WebForm and Razor view engines. You can also register your own custom view engine to your Asp.Net MVC application as shown below:

   protected void Application_Start() 
   { 
    //Remove All View Engine including Webform and Razor
    ViewEngines.Engines.Clear();
    //Register Your Custom View Engine
    ViewEngines.Engines.Add(new CustomViewEngine());
    //Other code is removed for clarity
   } 
   

7. View

   The action method may return a text string, a binary file, or JSON formatted data. The most important Action Result is the ViewResult, which renders and returns an HTML page to the browser using the current view engine.

Summary

I hope you will enjoy the Asp.Net MVC request life cycle while programming with Asp.Net MVC. I would like to have feedback from my blog readers. Your valuable feedback, questions, or comments about this article are always welcome. To delve deep into the core concepts of MVC, consider enrolling in our ASP.NET MVC Certification Course to get your hands on a comprehensive guide.

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