MVC Q&A

Dear readers, these ASP.NET MVC Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of ASP.NET MVC. As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer:

  • Breifly explain us what is ASP.Net MVC?
    ASP.Net MVC is a pattern which is used to split the application’s implementation logic into three components i.e. models, views, and controllers.
  • Tell us something about Model, view and Controllers in Asp.Net MVC?
    Model : It is basically a business entity which is used to represent the application data. Controller : The Request which is sent by the user always scatters through controller and it’s responsibility is to redirect to the specific view using View () method. View : it’s the presentation layer of ASP.Net MVC.
  • Do you know about the new features in ASP.Net MVC 4 (ASP.Net MVC4)?
    Following are features added newly : Mobile templates Added ASP.NET Web API template for creating REST based services. Asynchronous controller task support. Bundling of the java scripts. Segregating the configs for ASP.Net MVC routing, Web API, Bundle etc.
  • How does the ‘page lifecycle’ of ASP.Net MVC works?
    Below are the processed followed in the sequence –
    App initialization
    Routing
    Instantiate and execute controller
    Locate and invoke controller action
    Instantiate and render view.
  • Explain the advantages of ASP.Net MVC over ASP.NET?
    • Provides a clean separation of concerns among UI (Presentation layer), model (Transfer objects/Domain Objects/Entities) and Business Logic (Controller).
    • Easy to UNIT Test.
    • Improved reusability of model and views. We can have multiple views which can point to the same model and vice versa.
    • Improved structuring of the code.
  • What is Separation of Concerns in ASP.NET ASP.Net MVC?
    It is the process of breaking the program into various distinct features which overlaps in functionality as little as possible. ASP.Net MVC pattern concerns on separating the content from presentation and data-processing from content.
  • What is Razor View Engine?
    Razor is the first major update to render HTML in ASP.Net MVC 3. Razor was designed specifically for view engine syntax. Main focus of this would be to simplify and code-focused templating for HTML generation. Below is the sample of using Razor:

    @model ASP.Net MVCMusicStore.Models.Customer
    @{ViewBag.Title = "Get Customers";}
    < div class="cust">
    <h3><em>@Model.CustomerName</<em> </
    <h3>
    <div>
    
  • What is the meaning of Unobtrusive JavaScript? Explain us by any practical example.
    This is a general term that conveys a general philosophy, similar to the term REST (Representational State Transfer). Unobtrusive JavaScript doesn’t inter mix JavaScript code in your page markup. Eg : Instead of using events like onclick and onsubmit, the unobtrusive JavaScript attaches to elements by their ID or class based on the HTML5 data- attributes.
  • What is the use of View Model in ASP.Net MVC?
    View Model is a plain class with properties, which is used to bind it to strongly typed view. View Model can have the validation rules defined for its properties using data annotations.
  • What you mean by Routing in ASP.Net MVC?
    Routing is a pattern matching mechanism of incoming requests to the URL patterns which are registered in route table. Class : “UrlRoutingModule” is used for the same process.
  • What are Actions in ASP.Net MVC?
    Actions are the methods in Controller class which is responsible for returning the view or json data. Action will mainly have return type : “ActionResult” and it will be invoked from method : “InvokeAction()” called by controller.
  • What is ViewData?
    Viewdata contains the key, value pairs as dictionary and this is derived from class : “ViewDataDictionary”. In action method we are setting the value for viewdata and in view the value will be fetched by typecasting.
  • What is the difference between ViewBag and ViewData in ASP.Net MVC?
    ViewBag is a wrapper around ViewData, which allows to create dynamic properties. Advantage of viewbag over viewdata will be : In ViewBag no need to typecast the objects as in ViewData. ViewBag will take advantage of dynamic keyword which is introduced in version 4.0. But before using ViewBag we have to keep in mind that ViewBag is slower than ViewData.
  • Explain TempData in ASP.Net MVC?
    TempData is again a key, value pair as ViewData. This is derived from “TempDataDictionary” class. TempData is used when the data is to be used in two consecutive requests, this could be between the actions or between the controllers. This requires typecasting in view.
  • What are HTML Helpers in ASP.Net MVC?
    HTML Helpers are like controls in traditional web forms. But HTML helpers are more lightweight compared to web controls as it does not hold viewstate and events. HTML Helpers returns the HTML string which can be directly rendered to HTML page. Custom HTML Helpers also can be created by overriding “HtmlHelper” class.
  • What is PartialView in ASP.Net MVC?
    PartialView is similar to UserControls in traditional web forms. For re-usability purpose partial views are used. Since it’s been shared with multiple views these are kept in shared folder. Partial Views can be rendered in following ways :

    • Html.Partial()
    • Html.RenderPartial()
  • What are AJAX Helpers in ASP.Net MVC?
    AJAX Helpers are used to create AJAX enabled elements like as Ajax enabled forms and links which performs the request asynchronously and these are extension methods of AJAXHelper class which exists in namespace – System.Web.ASP.Net MVC.
  • What are the options can be configured in AJAX helpers?
    Below are the options in AJAX helpers :

    • Url : This is the request URL.
    • Confirm : This is used to specify the message which is to be displayed in confirm box.
    • OnBegin : Javascript method name to be given here and this will be called before the AJAX request.
    • OnComplete : Javascript method name to be given here and this will be called at the end of AJAX request.
    • OnSuccess – Javascript method name to be given here and this will be called when AJAX request is successful.
    • OnFailure – Javascript method name to be given here and this will be called when AJAX request is failed.
    • UpdateTargetId : Target element which is populated from the action returning HTML.
  •  What is Layout in ASP.Net MVC?
    Layout pages are similar to master pages in traditional web forms. This is used to set the common look across multiple pages. In each child page we can find

    @{
    Layout = "~/Views/Shared/TestLayout1.cshtml";
    }
    

    This indicates child page uses TestLayout page as it’s master page.

  • Explain Sections is ASP.Net MVC?
    Section are the part of HTML which is to be rendered in layout page. In Layout page we will use the below syntax for rendering the HTML :

    @RenderSection("TestSection")
    

    And in child pages we are defining these sections as shown below :

    @section TestSection{
    Test Content
    }
    

    If any child page does not have this section defined then error will be thrown so to avoid that we can render the HTML like this :

    @RenderSection("TestSection", required: false)
    
  • Can you explain RenderBody and RenderPage in ASP.Net MVC?
    RenderBody is like ContentPlaceHolder in web forms. This will exist in layout page and it will render the child pages/views. Layout page will have only one RenderBody() method. RenderPage also exists in Layout page and multiple RenderPage() can be there in Layout page.
  • What is ViewStart Page in ASP.Net MVC?
    This page is used to make sure common layout page will be used for multiple views. Code written in this file will be executed first when application is being loaded.
  • Explain the methods used to render the views in ASP.Net MVC?
    Below are the methods used to render the views from action –

    • View() : To return the view from action.
    • PartialView() : To return the partial view from action.
    • RedirectToAction() : To Redirect to different action which can be in same controller or in different controller.
    • Redirect() : Similar to “Response.Redirect()” in webforms, used to redirect to specified URL.
    • RedirectToRoute() : Redirect to action from the specified URL but URL in the route table has been matched.
  • What are the sub types of ActionResult?
    ActionResult is used to represent the action method result. Below are the subtypes of ActionResult :

    • ViewResult
    • PartialViewResult
    • RedirectToRouteResult
    • RedirectResult
    • JavascriptResult
    • JSONResult
    • FileResult
    • HTTPStatusCodeResult
  • What are Non Action methods in ASP.Net MVC?
    In ASP.Net MVC all public methods have been treated as Actions. So if you are creating a method and if you do not want to use it as an action method then the method has to be decorated with “NonAction” attribute as shown below :

    [NonAction]
    public void TestMethod()
    {
    // Method logic
    }
    
  • How to change the action name in ASP.Net MVC?
    “ActionName” attribute can be used for changing the action name. Below is the sample code snippet to demonstrate more :

    [ActionName("TestActionNew")]
    public ActionResult TestAction()
        {
            return View();
        }
    

    So in the above code snippet “TestAction” is the original action name and in “ActionName” attribute, name – “TestActionNew” is given. So the caller of this action method will use the name “TestActionNew” to call this action.

  • What are Code Blocks in Views?
    Unlike code expressions that are evaluated and sent to the response, it is the blocks of code that are executed. This is useful for declaring variables which we may be required to be used later.

    @{
     int x = 123;
     string y = "aa";
     }
    
  • What is the “HelperPage.IsAjax” Property?
    The HelperPage.IsAjax property gets a value that indicates whether Ajax is being used during the request of the Web page.
  • What are Validation Annotations?
    Data annotations are attributes which can be found in the “System.ComponentModel.DataAnnotations” namespace. These attributes will be used for server-side validation and client-side validation is also supported. Four attributes – Required, String Length, Regular Expression and Range are used to cover the common validation scenarios.
  • Why to use Html.Partial in ASP.Net MVC?
    This method is used to render the specified partial view as an HTML string. This method does not depend on any action methods. We can use this like below : @Html.Partial(“TestPartialView”)
  • What is Html.RenderPartial?
    Result of the method : “RenderPartial” is directly written to the HTML response. This method does not return anything (void). This method also does not depend on action methods. RenderPartial() method calls “Write()” internally and we have to make sure that “RenderPartial” method is enclosed in the bracket. Below is the sample code snippet :

    @{Html.RenderPartial("TestPartialView"); }
    
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