ASP.NET MVC Interview Questions and Answers (42)

MVC stands for Model View Controller.
It divides an application into 3 component roles which is based on a framework methodology.
These component roles are discussed briefly as follows:

i) Models : These component roles are used to maintain the state which is persisted inside the Database.

Example: we might have a Product class that is used to represent order data from the Products table inside SQL.

ii) Views : These component roles are used to display the user interface of the application, where this UI is created off of the model data.

Example: we might create an Product “Edit” view that surfaces textboxes, dropdowns and checkboxes based on the current state of a Product object.

iii) Controllers : These component roles are used for various purposes like handling end user interaction, manipulating the model, and ultimately choosing a view to render to display UI.

Note:

In a MVC application, the views are used only for displaying the information whereas the controllers are used for handling and responding to user input and interaction.

The MVC framework is defined through System.Web.Mvc assembly.
This is because this is the only assembly which contains classes and interfaces that support the ASP.NET Model View Controller (MVC) framework for creating Web applications.

We can combine ASP.NET MVC into an existing ASP.NET application by following the below procedure:

First of all, you have to add a reference to the following three assemblies to your existing ASP.NET application:

i) System.Web.Routing
ii) System.Web.Abstractions
iii) System.Web.Mvc

The ASP.NET MVC folder should be created after adding these assembly references.
Add the folder Controllers, Views, and Views | Shared to your existing ASP.NET application.
And then you have to do the necessary changes in web.config file.
For this you can refer to the below link:

http://www.packtpub.com/article/mixing-aspnet-webforms-and-aspnet-mvc

The main advantages of using asp.net mvc are as follows:

i) One of the main advantage is that it will be easier to manage the complexity as the application is divided into model,view and controller.
ii) It gives us the full control over the behavior of an application as it does not use view state or server-based forms.
iii) It provides better support for test-driven development (TDD).
iv) You can design the application with a rich routing infrastructure as it uses a Front Controller pattern that processes Web application requests through a single controller.

This Razor View engine is a part of new rendering framework for ASP.NET web pages.
ASP.NET rendering engine uses opening and closing brackets to denote code (<% %>), whereas Razor allows a cleaner, implied syntax for determining where code blocks start and end.

Example:

In the classic renderer in ASP.NET:

<ul>

<% foreach (var userTicket in Model)

  { %>

    <li><%: userTicket.Value %></li>

<%  } %>

</ul> 

By using Razor:

<ul>

@foreach (var userTicket in Model)

{

  <li>@userTicket.Value</li>

}

</ul>

In an MVC application, all the features are based on interface. So, it is easy to unit test a MVC application.
And it is to note that, in MVC application there is no need of running the controllers for unit testing.

System.Web.Mvc namespace contains all the interfaces and classes which supports ASP.NET MVC framework for creating web applications.

Yes, It is possible to share a view across multiple controllers by putting a view into the shared folder.
By doing like this, you can automatically make the view available across multiple controllers.

A controller will decide what to do and what to display in the view. It works as follows:

i) A request will be received by the controller
ii) Basing on the request parameters, it will decide the requested activities
iii) Basing on the request parameters, it will delegates the tasks to be performed
iv) Then it will delegate the next view to be shown

An action method is used to return an instance of any class which is derived from ActionResult class.
Some of the return types of a controller action method are:
i) ViewResult : It is used to return a webpage from an action method
ii) PartialViewResult : It is used to send a section of a view to be rendered inside another view.
iii) JavaScriptResult : It is used to return JavaScript code which will be executed in the user’s browser.
iv) RedirectResult : Based on a URL, It is used to redirect to another controller and action method.
v) ContentResult : It is an HTTP content type may be of text/plain. It is used to return a custom content type as a result of the action method.
vi) JsonResult : It is used to return a message which is formatted as JSON.
vii) FileResult : It is used to send binary output as the response.
viii) EmptyResult : It returns nothing as the result.

The page lifecycle of an ASP.NET MVC page is explained as follows:

i) App Initialisation
In this stage, the aplication starts up by running Global.asax’s Application_Start() method.
In this method, you can add Route objects to the static RouteTable.Routes collection.
If you’re implementing a custom IControllerFactory, you can set this as the active controller factory by assigning it to the System.Web.Mvc.ControllerFactory.Instance property.

ii) Routing
Routing is a stand-alone component that matches incoming requests to IHttpHandlers by URL pattern.
MvcHandler is, itself, an IHttpHandler, which acts as a kind of proxy to other IHttpHandlers configured in the Routes table.

iii) Instantiate and Execute Controller
At this stage, the active IControllerFactory supplies an IController instance.

iv) Locate and invoke controller action
At this stage, the controller invokes its relevant action method, which after further processing, calls RenderView().

v) Instantiate and render view
At this stage, the IViewFactory supplies an IView, which pushes response data to the IHttpResponse object.

It is already known that all the public methods of a controller class are basically treated as action methods.
If you dont want this default behaviour, then you can change the public method with NonActionAttribute. Then, the default behaviour changes.

The Router Table is formed by following the below procedure:

In the begining stage, when the ASP.NET application starts, the method known as Application_Start() method is called.
The Application_Start() will then calls RegisterRoutes() method.
This RegisterRoutes() method will create the Router table.