ASP.NET MVC PAGE LIFE CYCLE
What is ASP.NET
MVC: ASP.NET MVC is a part of the ASP.NET
Web application framework.
It is one of the two different programming models you can use to
create ASP.NET Web
applications, the other being ASP.NET Web
Forms.
An MVC Application is designed and implemented using the
following three attributes
• Model: The model contains
the core information for an application. This includes the data and validation rules as well as
data access and aggregation logic.
• View: The view encapsulates the presentation of the application, and in ASP.NET this is
typically the HTML markup.
• Controller: The controller contains
the control‐flow logic.
It interacts with the Model
and Views to control the flow of
information and execution of the
application.
Page Life Cycle of ASP.NET MVC
Requests to an ASP.NET MVC‐based Web application first pass through the UrlRoutingModule object, which is an HTTP module. This module parses the request and performs route selection.
The UrlRoutingModule object selects
the first route object that matches the current request. (A route object is a class that implements RouteBase, and is typically
an instance of the Route
class.) If no routes match, the UrlRoutingModule object does nothing and lets the request fall back to the regular ASP.NET or IIS request processing. From the selected Route object, the UrlRoutingModule object obtains
the IRouteHandler object that is associated with the Route object. Typically, in an MVC application, this will
be an instance of MvcRouteHandler. The IRouteHandler instance creates an IHttpHandler object and
passes
it the IHttpContext object. By default, the IHttpHandler instance for MVC is the
MvcHandler object. The MvcHandler object then selects
the controller that will ultimately handle the request.
The module and handler are the entry points to the ASP.NET MVC framework. They perform the following actions:
• Select the appropriate controller in an MVC Web application.
• Obtain a specific controller
instance.
• Call the controller's Execute
method.
The following table lists the stages of
execution for an MVC Web project.
Stage
|
Details
|
Receive
first
request for the application
|
In the Global.asax file, Route objects are
added to the RouteTable object.
|
Perform
routing
|
The UrlRoutingModule module uses the first matching Route object in the
RouteTable collection to create the RouteData object, which it then
uses to create a RequestContext (IHttpContext)
object.
|
Create MVC
request handler
|
The MvcRouteHandler object creates an instance of the
MvcHandler class
and passes it
the RequestContext instance.
|
Create
controller
|
The MvcHandler object uses the RequestContext instance to
identify the IControllerFactory object (typically an instance of the DefaultControllerFactory class) to create the controller instance with.
|
Execute
controller
|
The MvcHandler instance calls the controller's Execute
method.
|
Invoke action
|
Most controllers inherit from the Controller base class. For controllers that do
so, the ControllerActionInvoker object that is associated
with the controller
determines which action method of the controller class to call, and then calls
that method.
|
Execute result
|
A typical action method might
receive user input,
prepare the appropriate
response data, and then execute the result
by returning a result type.
The built‐in result types that can be executed include the following: ViewResult
(which renders
a view and is the most‐often used result
type), RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, and EmptyResult.
|
Figure 1: ASP.NET MVC Request
A URL Does Not Equal a Page
When you build a traditional ASP.NET Web Forms application or an Active
Server Pages application, there is a one‐to‐one correspondence between a URL and a page. If you request a page named SomePage.aspx from the server, then there had better be a page on disk named SomePage.aspx. If the SomePage.aspx file does
not exist, you get an ugly 404 – Page Not Found error. When building an ASP.NET MVC application, in contrast, there is no correspondence between the URL that you type into your browser’s address bar and the files that you find in your application. In an ASP.NET MVC application, a URL corresponds to a controller action
instead of a page on disk. In a traditional ASP.NET or ASP application, browser requests are mapped to pages. In an ASP.NET MVC application, in contrast,
browser requests are mapped to controller
actions. An ASP.NET Web Forms application is content‐centric. An ASP.NET MVC application, in contrast, is application logic centric.
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