MVC Interview Questions and Answers

What are the 3 main components of an ASP.NET MVC application?
1. M - Model
2. V - View
3. C - Controller

In which assembly is the MVC framework defined?
System.Web.Mvc

Is it possible to combine ASP.NET webforms and ASP.MVC and develop a single web application?
Yes, it is possible to combine ASP.NET webforms and ASP.MVC and develop a single web application.

What does Model, View and Controller represent in an MVC application?
Model: Model represents the application data domain. In short the applications business logic is contained with in the model.

View: Views represent the user interface, with which the end users interact. In short the all the user interface logic is contained with in the UI.

Controller: Controller is the component that responds to user actions. Based on the user actions, the respective controller, work with the model, and selects a view to render that displays the user interface. The user input logic is contained with in the controller.

What is the greatest advantage of using asp.net mvc over asp.net webforms?
It is difficult to unit test UI with webforms, where views in mvc can be very easily unit tested.

Which approach provides better support for test driven development - ASP.NET MVC or ASP.NET Webforms?
ASP.NET MVC

What are the advantages of ASP.NET MVC?
1. Extensive support for TDD. With asp.net MVC, views can also be very easily unit tested.
2. Complex applications can be easily managed
3. Seperation of concerns. Different aspects of the application can be divided into Model, View and Controller.
4. ASP.NET MVC views are light weight, as they donot use viewstate.

Is it possible to unit test an MVC application without running the controllers in an ASP.NET process?
Yes, all the features in an asp.net MVC application are interface based and hence mocking is much easier. So, we don't have to run the controllers in an ASP.NET process for unit testing.

Is it possible to share a view across multiple controllers?
Yes, put the view into the shared folder. This will automatically make the view available across multiple controllers.

What is the role of a controller in an MVC application?
The controller responds to user interactions, with the application, by selecting the action method to execute and alse selecting the view to render.

Where are the routing rules defined in an asp.net MVC application?
In Application_Start event in Global.asax

Name a few different return types of a controller action method?
The following are just a few return types of a controller action method. In general an action method can return an instance of a any class that derives from ActionResult class.
1. ViewResult
2. JavaScriptResult
3. RedirectResult
4. ContentResult
5. JsonResult

What is the significance of NonActionAttribute?
In general, all public methods of a controller class are treated as action methods. If you want prevent this default behaviour, just decorate the public method with NonActionAttribute.

What is the significance of ASP.NET routing?
ASP.NET MVC uses ASP.NET routing, to map incoming browser requests to controller action methods. ASP.NET Routing makes use of route table. Route table is created when your web application first starts. The route table is present in the Global.asax file.

What are the 3 segments of the default route, that is present in an ASP.NET MVC application?
1st Segment - Controller Name
2nd Segment - Action Method Name
3rd Segment - Parameter that is passed to the action method

ASP.NET MVC application, makes use of settings at 2 places for routing to work correctly. What are these 2 places?
1. Web.Config File : ASP.NET routing has to be enabled here.
2. Global.asax File : The Route table is created in the application Start event handler, of the Global.asax file.

What is the adavantage of using ASP.NET routing?
In an ASP.NET web application that does not make use of routing, an incoming browser request should map to a physical file. If the file does not exist, we get page not found error.

An ASP.NET web application that does make use of routing, makes use of URLs that do not have to map to specific files in a Web site. Because the URL does not have to map to a file, you can use URLs that are descriptive of the user's action and therefore are more easily understood by users.

What are the 3 things that are needed to specify a route?
1. URL Pattern - You can include placeholders in a URL pattern so that variable data can be passed to the request handler without requiring a query string.
2. Handler - The handler can be a physical file such as an .aspx file or a controller class.
3. Name for the Route - Name is optional.

Is the following route definition a valid route definition?
{controller}{action}/{id}
No, the above definition is not a valid route definition, because there is no literal value or delimiter between the placeholders. Therefore, routing cannot determine where to separate the value for the controller placeholder from the value for the action placeholder.

What is the use of the following default route?
{resource}.axd/{*pathInfo}
This route definition, prevent requests for the Web resource files such as WebResource.axd or ScriptResource.axd from being passed to a controller.

What is the difference between adding routes, to a webforms application and to an mvc application?
To add routes to a webforms application, we use MapPageRoute() method of the RouteCollection class, where as to add routes to an MVC application we use MapRoute() method.

How do you handle variable number of segments in a route definition?
Use a route with a catch-all parameter. An example is shown below. * is referred to as catch-all parameter.
controller/{action}/{*parametervalues}

What are the 2 ways of adding constraints to a route?
1. Use regular expressions
2. Use an object that implements IRouteConstraint interface

Give 2 examples for scenarios when routing is not applied?
1. A Physical File is Found that Matches the URL Pattern - This default behaviour can be overriden by setting the RouteExistingFiles property of the RouteCollection object to true.
2. Routing Is Explicitly Disabled for a URL Pattern - Use the RouteCollection.Ignore() method to prevent routing from handling certain requests.

What is the use of action filters in an MVC application?
Action Filters allow us to add pre-action and post-action behavior to controller action methods.

If I have multiple filters impleted, what is the order in which these filters get executed?
1. Authorization filters
2. Action filters
3. Response filters
4. Exception filters

What are the different types of filters, in an asp.net mvc application?
1. Authorization filters
2. Action filters
3. Result filters
4. Exception filters

Give an example for Authorization filters in an asp.net mvc application?
1. RequireHttpsAttribute
2. AuthorizeAttribute

Which filter executes first in an asp.net mvc application?
Authorization filter


What are the levels at which filters can be applied in an asp.net mvc application?
1. Action Method
2. Controller
3. Application
[b]Is it possible to create a custom filter?[/b]
Yes

What filters are executed in the end?
Exception Filters

Is it possible to cancel filter execution?
Yes

What type of filter does OutputCacheAttribute class represents?
Result Filter

What are the 2 popular asp.net mvc view engines?
1. Razor
2. .aspx

What symbol would you use to denote, the start of a code block in razor views?
@

What symbol would you use to denote, the start of a code block in aspx views?
<%= %>

In razor syntax, what is the escape sequence character for @ symbol?
The escape sequence character for @ symbol, is another @ symbol

When using razor views, do you have to take any special steps to proctect your asp.net mvc application from cross site scripting (XSS) attacks?
No, by default content emitted using a @ block is automatically HTML encoded to protect from cross site scripting (XSS) attacks.

When using aspx view engine, to have a consistent look and feel, across all pages of the application, we can make use of asp.net master pages. What is asp.net master pages equivalent, when using razor views?
To have a consistent look and feel when using razor views, we can make use of layout pages. Layout pages, reside in the shared folder, and are named as _Layout.cshtml

What are sections?
Layout pages, can define sections, which can then be overriden by specific views making use of the layout. Defining and overriding sections is optional.

What are the file extensions for razor views?
1. .cshtml - If the programming lanugaue is C#
2. .vbhtml - If the programming lanugaue is VB

How do you specify comments using razor syntax?
Razor syntax makes use of @* to indicate the begining of a comment and *@ to indicate the end. An example is shown below.
@* This is a Comment *@

Difference between IQueriable and IEnumberable?

What are the different Filters? - 1. Authorization 2. Action filter 3. Result 4. Exception (all are in sequence in excecution)

MVC Introduction

What is MVC ?

MVC is a framework pattern that divides an application’s implementation logic into three component as : Models, Views, and Controllers

1. Model: 

The business entity on which the overall application operates. Many applications use a persistent storage mechanism (such as a database) to store data.MVC does not specifically mention the data access layer because it is understood to be encapsulated by the Model.

The model represents core business logic and data. Models encapsulate the properties and behavior of a domain entity and expose properties that describe the entity. for the Auction class represents the concept of an “auction” in the application

2. View: 

The user interface that renders the Model into a form of interaction.

The view is responsible for transforming a model or models into a visual representation.  web applications, this most often means generating HTML to be rendered in the browser, although views can manifest in many forms.

For instance, the same might be visualized in HTML, PDF, XML, or perhaps even in a spreadsheet.

Following separation of concerns, views should concentrate only on displaying data should not contain any business logic themselves—the business logic stays in the, which should provide the view with everything it needs.

3. Controller: 

Handles a request from a View and updates the Model that results in a change of the Model's state. The controller, as the name implies, controls the application logic and acts as the coordinator the view and the model.

Controllers receive input from users via the, then work with the model to perform specific actions, passing the results back to view.

Microsoft’s Web Development Platforms:

Microsoft has given the development community several web development platforms as follows:

Active Server Pages (ASP):

Microsoft’s first answer to web development was Active Server Pages (ASP), a scripting language in which code and markup are authored together in a single file, with each physical file corresponding to a page on the website.

ASP’s server-side scripting approach widely popular and many websites grew out of it. Some of these sites to serve visitors today. After a while, though, developers wanted more.

They for features such as improved code reuse, better separation of concerns, and application of object-oriented programming principles. In 2002, Microsoft ASP.NET as a solution to these concerns.

ASP.NET Web Forms:

Like ASP, ASP.NET websites rely on a page-based approach where each page on the is represented in the form of a physical file (called a Web Form) and is accessible that file’s name.

Unlike a page using ASP, a Web Forms page provides some of code and markup by splitting the web content into two different files:

One for the markup and one for the code. ASP.NET and the Web Forms approach developers’ needs for many years, and this continues to be the web development of choice for many .NET developers.

Some .NET developers, however, the Web Forms approach too much of an abstraction from the underlying, JavaScript, and CSS.

ASP.NET MVC:

Microsoft was quick to spot the growing need in the ASP.NET developer community something different than the page-based Web Forms approach, and the company the first version of ASP.NET MVC in 2008.

Representing a total departure the Web Forms approach, ASP.NET MVC abandons the page-based architecture, relying on the Model-View-Controller (MVC) architecture instead.