MVC



1. What is MVC pattern?  

The main purpose using MVC pattern is to decouple the GUI from the Data. It also gives the ability to provide multiple views for the same Data. MVC pattern separates objects in to three important sections:- • Model: - This section is specially for maintaining data. It is actually where your business logic, querying database, database connection etc. is actually implemented. • Views: - Displaying all or some portion of data, or probably different view of data. View is responsible for look and feel, Sorting, formatting etc. • Controller: - They are event-handling section, which affects either the model or the view. Controller responds to the mouse or keyboard input to command model and view to change. Controllers are associated with views. User interaction triggers the events to change the model, which in turn calls some methods of model to update its state to notify other registered views to refresh their display.


2. What does MVC means ?  


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.



3. Which assembly is used to define the MVC framework and Why ?  

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.


4. How can we plug an ASP.NET MVC into an existing ASP.NET application ?  

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.



5. What are the advantages of using asp.net 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.


6. Explain about Razor View Engine ?  

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:
br><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>


7. Does the unit testing of an MVC application is possible without running controllers in an ASP.NET process ?  

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.


8. Which namespace is used for ASP.NET MVC ?  

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


9. Can we share a view across multiple controllers ?  

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.


10. What is the use of a controller in an MVC application ?  

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


11. Mention some of the return types of a controller action method ?  

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 ontroller 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.


12. Explain about page life cycle of ASP.NET MVC ?  

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

i) App Initialisationbr>In this stage, the aplication starts up by running Global.asax’sApplication_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.


13. Explain about NonActionAttribute ?  

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.


14. In an MVC application, what are the segments of the default route ?  

There are 3 segments of the default route in an MVC application.Theyare:

The 1st segment is the Controller Name.
Example: search

The 2nd segment is the Action Method Name.
Example: label

The 3rd segment is the Parameter passed to the Action method.
Example: Parameter Id - MVC


15. What are the settings to be done for the Routing to work properly in an MVC application ?  

The settings must be done in 2 places for the routing to work properly.Theyare:

i) Web.Config File : In the web.config file, the ASP.NET routing has to be enabled.
ii) Global.asax File : The Route table is created in the application Start event handler, of the Global.asax file.


16. How to avoid XSS Vulnerabilities in ASP.NET MVC ?  

To avoid xss vulnerabilities, you have to use the syntax as '<%: %>' in ASP.NET MVC instead of using the syntax as '<%= %>' in .net framework 4.0.
This is because it does the HTML encoding.

Example:

<input type="text" value="<%: value%>" />



17. What are the things that are required to specify a route ?  

There are 3 things that are required to specify a route.

i) URL Pattern : You can pass the variable data to the request handler without using a query string. This is done by including placeholders in a URL pattern.
ii) Handler : This handler can be a physical file of 2 types such as a .aspx file or a controller class.
iii) Name for the Route : This name is an optional thing.


18. Explain the difference between adding routes, to a web application and to an mvcapplication ?  

We use MapPageRoute() method of a RouteCollection class for adding routes to a webforms application, whereas MapRoute() method is used to add routes to an MVC application.


19. Explain the usage of action filters in an MVC application ?  

Action filter in an mvc application is used to perform some additional processing, such as providing extra data to the action method, inspecting the return value, or canceling execution of the action method.
Action filter is an attribute that implements the abstract FilterAttribute class.


20. What is partial view in Asp.Net Mvc?  

A partial view is like as user control in Asp.Net web form. Partial views are reusable views like as Header and Footer. It has .csHtml extension.
Partial and RenderPartial Html method renders partial view in Mvc razor.
@Html.Partial("_Comments")

@ { Html.RenderPartial("_Comments") }


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