Posted By: P.K.S
8/17/2013 12:00:00 AM
language: Asp.net MVC
1. Can you describe ASP.NET MVC Request Life Cycle?
Ans. There are two answers for the question.
Short Answer: Following are the steps that are executed in ASP.NET MVC Request
I. Receive request, look up Route object in RouteTable collection and create
II. Create RequestContext instance.
III. Create MvcHandler and pass RequestContext to handler.
IV. Identify IControllerFactory from RequestContext.
V. Create instance of class that implements ControllerBase.
VI. Call MyController.Execute method.
VII. The ControllerActionInvoker determines which action to invoke on the controller
and executes the action on the controller, which results in calling the model and
returning a view.
Detailed Answer: There are five main steps occurs in ASP.NET Request Life
I. Initialize Application (Route table is created)
Desc. When we request a page from a normal ASP.NET application, there is a
physical copy of page on the disk that is corresponds to each page request. In
ASP.NET MVC, there is no page on the disk that corresponds to the request.
Request is routed to the controller. The controller is responsible for generating page
that is sent back to the browser.
ASP.NET MVC has Route Table which stores mapping entries of particular URLs to
action methods of contoller. i.e. URL “http://jinaldesai.net/Articles/CSharp” maps to
the “CSharp” method of “Articles” controller.
In ASP.NET MVC application like normal ASP.NET application when application
starts first time, it calls Application_Start() application event from Global.asax. Route
table is registered(created) from Appication_Start() event.
II. Routing Mechanism (UrlRoutingModule intercepts the request)
When a request is coming to ASP.NET MVC application, the request is intercepted
by UrlRoutingModule HTTP Module. The first thing the module does is to wrap up the
current HttpContext in an HttpContextWrapper2 object. Next, the module passes the
wrapped HttpContext to the RouteTable that was setup in the previous step, which
includes includes the URL, form parameters, query string parameters, and cookies
associated with the current request.
Next, the module creates a RouteContext object that represents the current
HttpContext and RouteData. The module then instantiates a new HttpHandler based
on the RouteTable and passes the RouteContext to the new handler’s constructor(In
ASP.NET MVC case it is MvcHandler).
Last step taken by module is setting MvcHandler as the current HTTP Handler.
III. MvcHandler Executes (Instantiate and execute controller)
In normal ASP.NET application after second step, it fires set of events including
Start, BeginRequest, PostResolveRequestCache, etc.
While in case of ASP.NET MVC application, MvcHandler(which is created in
previous step) creates appropriate controller instance to serve the request by
passing controller name(found through the route mapping table) and
RequestContext to the static method CreateController() method of ControllerFactory
class(i.e. ControllerFactory.CreateController()) to get particular controller.
Next is ControllerContext object is created from the RequestContext and the
controller. And the last step in Step 3 is the Execute() method is called on the
controller class.(Here factory pattern is implemented)
IV. Controller Executes (Locate and invoke controller action)
The Controller.Execute() method takes RouteData and other context information to
locate appropriate action method. It also maps incoming request
parameters(querystring, form, etc) to the parameter list of the controller action
Next is the controller calls it’s InvokeAction() method, passing details of the choosen
action method and invokes the action method and our code finally runs.
V. RenderView Method Invoked (Instantiate and render view)
The controller object created in previous step has a property ViewFactory of type
IViewFactory. The IViewFactory has a method CreateView(), which is called next by
passing view name and other context information. The CreateView() method returns
Next the controller invokes RenderView() method of returned IView with again
supplying necessary context information includes ViewData and IHttpResponse
object. The response data is a HTML, an image, or any other binary or text data.
2. What is MVP?
Ans. MVP(Model View Presentor) is a user interface design pattern engineered to
facilitate automated unit testing and improve the separation of concerns in
It is derived from MVC(Model View Controller) design pattern. The MVP in the pattern
has following description.
The model is an interface defining the data to be displayed or otherwise acted upon
in the user interface.
The view is an interface that displays data (the model) and routes user commands
(events) to the presenter to act upon that data.
The presenter acts upon the model and the view. It retrieves data from repositories
(the model), and formats it for display in the view.
3. What is difference between MVC and MVP?
Ans. The key difference between MVC and MVP is that MVP truly separates the UI
from the domain/service layer of the application. In MVP the presenter assumes the
functionality of the middle-man(played by the Controller in MVC). MVP is specially
geared towards a page event model such as ASP.NET.
For more differences see my article: MVC Vs MVP
4. What is Application Areas in ASP.NET MVC application? Why it is
Ans. An Area in ASP.NET MVC application is subset of the project structure based
on a logical grouping. Each area contains area specific models, views and
controllers. In ASP.NET MVC we can use the default project structure for most
websites without having any problems. However, there are some sites that are very
large; keeping all the models, views and controllers in a single folder set can be
difficult to manage. For such cases, we can define different project ares in ASP.NET
5. What are the different return types controller action method supports in
Ans. There are total nine return types we can use to return results from controller to
view. The base type of all these result types is ActionResult.
ViewResult (View) : Used to return a webpage from an action method.
PartialviewResult (Partialview) : Used to send a section of a view to be rendered
inside another view.
RedirectResult (Redirect) : Used to redirect to another controller and action
based on a URL.
RedirectToRouteResult (RedirectToAction, RedirectToRoute) : Used to
another action method.
ContentResult (Content) : Used to return a custom content type as the result of
action method. This is an HTTP content type, such as text/plain.
jsonResult (json) : Used to return a message formatted as JSON.
in the user’s browser.
FileResult (File) : Used to send binary output as the response.
EmptyResult : Used to return nothing (void) as the result.
6. What is action filters in ASP.NET MVC?
Ans. In ASP.NET MVC we can run our code before controller’s action method is
executed or after the action method run. To achieve this we can use action filters.
We can apply action filters by applying attributes to action methods.
7. Can you describe different types of action filters in brief?
Ans. There are mainly three types of action filters provided in ASP.NET MVC.
Authorization Filter : It makes security decisions about whether to execute an
action method, such as performing authentication or validating properties of the
request. The AuthorizeAttribute class is one example of an authorization filter.
Result Filter : It wraps execution of the ActionResult object. This filter can perform
additional processing of the result, such as modifying the HTTP response. The
OutputCacheAttribute class is one example of a result filter.
Execution Filter : It executes if there is an unhandled exception thrown somewhere
in action method, starting with the authorization filters and ending with the execution
of the result. Exception filters can be used for tasks such as logging or displaying an
error page. The HandleErrorAttribute class is one example of an exception filter.
Apart from the readymade action filters provided by ASP.NET MVC, you can also
implement your own action filter by inheriting ActionFilterAttribute abstract class. It
has four virtual methods that you can override: OnActionExecuting,
OnActionExecuted, OnResultExecuting and OnResultExecuted. To implement an
action filter, you must override at least one of these methods.
8. What are the enhancements ASP.NET MVC 3 provided compared to
ASP.NET MVC 2?
Ans. There are many enhancements come with ASP.NET MVC 3. Following are list
of some enhancements in ASP.NET MVC 3.
Razor View Engine
Partial Page Output Caching
New Dynamic ViewModel Property
New ActionResult Types (HttpNotFoundResult, HttpStatusCodeResult,
Built in JSON binding support
9. What is Data Annotations?
Ans. Data Annotations are validation mechanism we can use to validate our data
stored in form of Entity Data Model, LINQ to SQL or any other data models. We can
use it in form of attributes to our properties of mode class. These attributes provide
common validation patterns, such as range checking and required fields. Once we
apply these attributes to our model class, ASP.NET MVC will provide both client and
server side validation checks with no additional coding required. You can also
implement your custom Data Annotation Validator by inheriting ValidationAttribute
class and overriding IsValid method. To name a few there is RangeAttribute,
RequiredAttribute, StringLengthAttribute, RegularExpressionAttribute, etc
10. What are HTML Helpers in ASP.NET MVC?
Ans. In MVC, HTML Helpers are much like traditional ASP.NET web form controls.
Just like web form controls in ASP.NET, HTML helpers are used to modify HTML.
But HTML helpers are more lightweight. Unlike Web Form controls, an HTML helper
does not have an event model and a view state. In most cases, an HTML helper is
just a method that returns a string. With MVC, you can create your own helpers, or
use the built in HTML helpers. To name a few there is BeginForm(), EndForm(),
TextBox(), TextArea(), ListBox(), RadioButton(), etc.
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