Asp.net MVC Interview Question and answers

What is MVC (Model View Controller)?

Let us understand this MVC is an architectural pattern which separates the representation and user interaction. It’s divided into three broader sections, Model, View, and Controller. Below is how each one of them handles the task.

• The View is responsible for the look and feel.
• Model represents the real world object and provides data to the View.
• The Controller is responsible for taking the end user request and loading the appropriate Model and View.

Types of Filters in ASP.NET MVC and their Sequence of Execution

1. Authentication Filters:
   Actually Authentication filter runs before any other filter or action method. Authentication confirms that you are a valid or invalid user. Action filters implements the IAuthenticationFilter interface. 
   
2. Authorization Filters:
   The AuthorizeAttribute and RequireHttpsAttribute are the examples of Authorization Filters. Authorization Filters are responsible for checking User Access; these implement the IAuthorizationFilterinterface in the framework. These filters used to implement authentication and authorization for controller actions. For example, the Authorize filter is an example of an Authorization filter.
3. Action Filters: 
   
   Action Filter is an attribute that you can apply to a controller action or an entire controller. This filter will be called before and after the action starts executing and after the action has executed.
   Action filters implement the IActionFilter interface that have two methods OnActionExecuting andOnActionExecuted. OnActionExecuting runs before the Action and gives an opportunity to cancel the Action call. These filters contain logic that is executed before and after a controller action executes, you can use an action filter, for instance, to modify the view data that a controller action returns.
4. Result Filters: 
   The OutputCacheAttribute class is an example of Result Filters. These implement the IResultFilter interface which like the IActionFilter has OnResultExecuting and OnResultExecuted. These filters contains logic that is executed before and after a view result is executed. Like if you want to modify a view result right before the view is rendered to the browser.
5. ExceptionFilters:
   The HandleErrorAttribute class is an example of ExceptionFilters. These implement the IExceptionFilter interface and they execute if there are any unhandled exceptions thrown during the execution pipeline. These filters can be used as an exception filter to handle errors raised by either your controller actions or controller action results.

What is routing in MVC?

 Actually Routing is a mechanism in MVC that decides which action method of a controller class to execute. Without routing there's no way an action method can be mapped. to a request. Routing is a part of the MVC architecture so ASP.NET MVC supports routing by default.

 routes.MapRoute(

               "View", // Route name
               "View/ViewCustomer/{id}", // URL with parameters
               new { controller = "Customer", action = "DisplayCustomer", 
id = UrlParameter.Optional }); // Parameter defaults   

Explain attribute based routing in MVC?

Let's understand this actually this  is a feature introduced in MVC 5. By using the "Route" attribute we can define the URL structure. For example in the below code we have decorated the "GotoAbout" action with the route attribute. The route attribute says that the "GotoAbout" can be invoked using the URL structure "Users/about".

public class HomeController : Controller
{
       [Route("Users/about")]
       public ActionResult GotoAbout()
       {
           return View();
       }
}

H

What is the advantage of defining route structures in the code?

Let's understand this deeply Most of the time developers code in the action methods. Developers can see the URL structure right upfront rather than going to the “routeconfig.cs” and see the lengthy codes. For instance in the below code the developer can see right upfront that the “GotoAbout” action can be invoked by four different URL structure.

This is much user friendly as compared to scrolling through the “routeconfig.cs” file and going through the length line of code to figure out which URL structure is mapped to which action.

public class HomeController : Controller

{
       [Route("Users/about")]
       [Route("Users/WhoareWe")]
       [Route("Users/OurTeam")]
       [Route("Users/aboutCompany")]
       public ActionResult GotoAbout()
       {
           return View();
       }
}

Let's understand what is the difference between tempdata, viewdata, and viewbag?

• Actually ViewBag and ViewData are used to communicate between controller and corresponding view. ..
• .ViewData is a dictionary object while ViewBag is a dynamic property (a new C# 4.0 feature).
• ViewData being a dictionary object is accessible using strings as keys and also requires typecasting for complex types.
• Temp data - Helps to maintain data when you move from one controller to another controller or from one action to another action. In other words when you redirect, tempdata helps to maintain data between those redirects. It internally uses session variables.
• View data - Helps to maintain data when you move from controller to view.
• View Bag - It’s a dynamic wrapper around view data. When you use Viewbag type, casting is not required. It uses the dynamic keyword internally.
• Session variables - By using session variables we can maintain data from any entity to any entity.
• Hidden fields and HTML controls - Helps to maintain data from UI to controller only. So you can send data from HTML controls or hidden fields to the controller using POST or GET HTTP methods.