MVC interview questions

The main objective of making use of Output Caching is to dramatically improve the performance of an ASP.NET MVC Application. It enables us to cache the content returned by any controller method so that the same content does not need to be generated each time the same controller method is invoked. Output Caching has huge advantages, such as it reduces server round trips, reduces database server round trips, reduces network traffic, etc.

A display mode is a powerful tool for all mobile-based apps development. However, it is not limited to mobile web apps but it can also be used to display any alternative view, which is tied to an existing controller. Display Modes practically give you another level of flexibility on top of the default capabilities we saw in the last section. Display Modes can also be used along with the previous feature so the users will simply build off of the site they just created. It simplifies the ways to implement different versions of view for different devices.

Default Route: The default ASP.NET MVC project templates add a generic route that uses the following URL convention to break the URL for a given request into three named segments.

URL: "{controller}/{action}/{id}"

This route pattern is registered via a call to the MapRoute() extension method of RouteCollection. 

Any web application has two main execution steps, first understanding the request and depending on the type of the request sending out an appropriate response. MVC application life cycle is not different it has two main phases, first creating the request object and second sending our response to the browser.

Creating the request object includes four basic steps: 

Step 1: Fill route
Step 2: Fetch route
Step 3: Request context created
Step 4: Controller instance created 

Action Filters are additional attributes that can be applied to either a controller section or the entire controller to modify the way in which action is executed. These attributes are special .NET classes derived from system attributes, which can be attached to classes, methods, properties, and fields.

Routing is a mechanism to process the incoming URL that is more descriptive and gives the desired response. In this case, URL is not mapped to specific files or folder, as was the case of websites in the past.

A partial view is a chunk of HTML that can be safely inserted into an existing DOM. Most commonly, partial views are used to componentize Razor views and make them easier to build and update. Partial views can also be returned directly from controller methods. In this case, the browser still receives text/HTML content but not necessarily HTML content that makes up an entire page. As a result, if a URL that returns a partial view is directly invoked from the address bar of a browser, an incomplete page may be displayed. This may be something like a page that misses title, script and style sheets.

TempData is a dictionary object to store data temporarily. It is a TempDataDictionary class type and instance property of the Controller base class. 
TempData can keep data for the duration of an HTTP request; in other words, it can keep live data between two consecutive HTTP requests. It will help us to pass the state between action methods. TempData only works with the current and subsequent request. TempData uses a session variable to store the data. TempData Requires type casting when used to retrieve data.

ASP.NET MVC has always supported the concept of “view engines” – which are the pluggable modules, which practically implement different template syntax options. The “default” view engine for ASP.NET MVC uses the same .aspx/.ascx/. master file templates as ASP.NET Web Forms. Other popular ASP.NET MVC view engines are Spart&Nhaml. Razor is the new view engine introduced by MVC 3.

Database First Approach is an alternative or substitutes to the Code First and Model First approaches to the Entity Data Model. The Entity Data Model creates model codes (classes, properties, DbContext, etc.) from the database in the project and that class behaves as the link between database and controller.

There are the following approaches, which are used to connect the database with the application.

• Database First
• Model First
• Code First

Bundling and minification are two new techniques introduced to improve request load time. It improves load time by reducing the number of requests to the server and reducing the size of requested assets (such as CSS and JavaScript).

Bundling: It lets us combine multiple JavaScript (.js) files or multiple cascading style sheet (.css) files so that they can be downloaded as a unit, rather than making individual HTTP requests.

Minification: It extracts the whitespace and performs other types of compression to make the downloaded files as small as possible. At runtime, the process recognizes the agent of the user, for example, IE, Mozilla, etc. and then removes whatever is specific to Mozilla when the request comes from IE.

ASP.NET Scaffolding is a code generation framework for ASP.NET Web applications. Visual Studio 2013 includes pre-installed code generators for MVC and Web API projects. You add scaffolding to your project when you want to quickly add code that interacts with data models. Using scaffolding can reduce the amount of time to develop standard data operations in your project.
Scaffolding consists of page templates, entity page templates, field page templates, and filter templates. These templates are called Scaffold templates and allow you to quickly build a functional data-driven Website.

In MVC 6 Microsoft removed the dependency of System.Web.Dll from MVC6 because it is extremely expensive, as it typically used to consume 30K of memory per request and response, whereas now MVC 6 only requires 2K of memory per request and the response is really small memory consumption.

 The Validation Summary helper method generates an unordered list (UL element) of validation messages that are in the Model State Dictionary object.

The Validation Summary can be used to display all the error messages for all the fields. It can also be used to display custom error messages. The following figure shows how Validation Summary displays the error messages.