Part - 3 : ASP.NET MVC Interview Question's Answer

11. What is difference between 3-layer architecture and MVC architecture?

3-layer architecture separates the application into 3 components which consists of Presentation Layer, Business Layer and Data Access Layer. In 3-layer architecture, user interacts with the Presentation layer. 3-layer is a linear architecture.
ASP.NET MVC 3 Tier Architecture
MVC architecture separates the application into three components which consists of Model, View and Controller. In MVC architecture, user interacts with the controller with the help of view. MVC is a triangle architecture
ASP.NET MVC Architecture
MVC does not replace 3-layer architecture. Typically 3-layer and MVC are used together and MVC acts as the Presentation layer.

12. What is difference between ASP.NET WebForm and ASP.NET MVC?

The main differences between ASP.NET Web Form and ASP.NET MVC are given below:

ASP.NET WebForms


ASP.NET Web Form follows a traditional event driven development model ASP.NET MVC is a lightweight and follow MVC (Model, View, and Controller) pattern based development model.
ASP.NET Web Form has server controls. ASP.NET MVC has html helpers.
ASP.NET Web Form has state management (like as view state, session) techniques. ASP.NET MVC has no automatic state management techniques.
ASP.NET Web Form has file-based URLs means file name exist in the URLs must have its physically existence. ASP.NET MVC has route-based URLs means URLs are divided into controllers and actions and moreover it is based on controller not on physical file.
ASP.NET Web Form follows WebForm Syntax ASP.NET MVC follow customizable syntax (Razor as default)
In ASP.NET Web Form, Web Forms (ASPX) i.e. views are tightly coupled to Code behind (ASPX.CS) i.e. logic. In ASP.NET MVC, Views and logic are kept separately.
ASP.NET Web Form has Master Pages for consistent look and feels. ASP.NET MVC has Layouts for consistent look and feels.
ASP.NET Web Form has User Controls for code reusability. ASP.NET MVC has Partial Views for code re-usability.
ASP.NET Web Form has built-in data controls and best for rapid development with powerful data access ASP.NET MVC is lightweight, provide full control over mark-up and support many features that allow fast & agile development. Hence it is best for developing interactive web application with latest web standards.
ASP.NET Web Form is not Open Source. ASP.NET Web MVC is an Open Source.

13. What is ViewModel in ASP.NET MVC?

In ASP.NET MVC, ViewModel is a class that contains the fields which are represented in the strongly-typed view. It is used to pass data from controller to strongly-typed view.
Key Points about ViewModel
  • ViewModel contain fields that are represented in the view (for LabelFor, EditorFor, DisplayFor helpers)
  • ViewModel can have specific validation rules using data annotations.
  • ViewModel can have multiple entities or objects from different data models or data source.

14. What is Routing in ASP.NET MVC?

Routing is a pattern matching system that monitor the incoming request and figure out what to do with that request. At runtime, Routing engine use the Route table for matching the incoming request's URL pattern against the URL patterns defined in the Route table. You can register one or more URL patterns to the Route table at Application_Start event mvc incoming request procesing by routing system

When the routing engine finds a match in the route table for the incoming request's URL, it forwards the request to the appropriate controller and action. If there is no match in the route table for the incoming request's URL, it returns a 404 HTTP status code.

15. Explain ASP.NET MVC pipeline?

The detail ASP.NET MVC pipeline is given below :
  1. Routing - Routing is the first step in ASP.NET MVC pipeline. Typically, it is a pattern matching system that matches the incoming request to the registered URL patterns in the Route Table.
    The UrlRoutingModule(System.Web.Routing.UrlRoutingModule) is a class which matches an incoming HTTP request to a registered route pattern in the RouteTable(System.Web.Routing.RouteTable). mvc pipeline
  2. Controller Initialization - The MvcHandler initiates the real processing inside ASP.NET MVC pipeline by using ProcessRequest method. This method uses the IControllerFactory instance (default is System.Web.Mvc.DefaultControllerFactory) to create corresponding controller.
  3. Action Execution – Action execution occurs in the following steps:
    • When the controller is initialized, the controller calls its own InvokeAction() method by passing the details of the chosen action method. This is handled by the IActionInvoker.
    • After chosen of appropriate action method, model binders(default is System.Web.Mvc.DefaultModelBinder) retrieves the data from incoming HTTP request and do the data type conversion, data validation such as required or date format etc. and also take care of input values mapping to that action method parameters.
    • Authentication Filter was introduced with ASP.NET MVC5 that run prior to authorization filter. It is used to authenticate a user. Authentication filter process user credentials in the request and provide a corresponding principal. Prior to ASP.NET MVC5, you use authorization filter for authentication and authorization to a user.
    • By default, Authenticate attribute is used to perform Authentication. You can easily create your own custom authentication filter by implementing IAuthenticationFilter.
    • Authorization filter allow you to perform authorization process for an authenticated user. For example, Role based authorization for users to access resources.
    • By default, Authorize attribute is used to perform authorization. You can also make your own custom authorization filter by implementing IAuthorizationFilter.
    • Action filters are executed before (OnActionExecuting) and after (OnActionExecuted) an action is executed. IActionFilter interface provides you two methods OnActionExecuting and OnActionExecuted methods which will be executed before and after an action gets executed respectively. You can also make your own custom ActionFilters filter by implementing IActionFilter. For more about filters refer this article Understanding ASP.NET MVC Filters and Attributes
    • When action is executed, it process the user inputs with the help of model (Business Model or Data Model) and prepare Action Result.
  4. Result Execution - Result execution occurs in the following steps:
    • Result filters are executed before (OnResultExecuting) and after (OnResultExecuted) the ActionResult is executed. IResultFilter interface provides you two methods OnResultExecuting and OnResultExecuted methods which will be executed before and after an ActionResult gets executed respectively. You can also make your own custom ResultFilters filter by implementing IResultFilter.
    • Action Result is prepared by performing operations on user inputs with the help of BAL or DAL. The Action Result type can be ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult.
    • Various Result type provided by the ASP.NET MVC can be categorized into two category- ViewResult type and NonViewResult type. The Result type which renders and returns an HTML page to the browser, falls into ViewResult category and other result type which returns only data either in text format, binary format or a JSON format, falls into NonViewResult category.
  5. View Initialization and Rendering - View Initialization and Rendering execution occurs in the following steps:
    • ViewResult type i.e. view and partial view are represented by IView (System.Web.Mvc.IView) interface and rendered by the appropriate View Engine.
    • This process is handled by IViewEngine (System.Web.Mvc.IViewEngine) interface of the view engine. By default ASP.NET MVC provides WebForm and Razor view engines. You can also create your custom engine by using IViewEngine interface and can registered your custom view engine in to your ASP.NET MVC application as shown below:
    • Html Helpers are used to write input fields, create links based on the routes, AJAX-enabled forms, links and much more. Html Helpers are extension methods of the HtmlHelper class and can be further extended very easily. In more complex scenario, it might render a form with client side validation with the help of JavaScript or jQuery
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