ASP.Net MVC Interview questions and Answers

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21) Explain TempData in 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.

22) What are HTML Helpers in 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.
23) What are AJAX Helpers in 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.Mvc.

24) 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.

25) What is Layout in 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 – /p>

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

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

26) Explain Sections is 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{
<h1>Test Content</h1>  } 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)

27) Can you explain RenderBody and RenderPage in 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.

28) What is ViewStart Page in 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.

29) Explain the methods used to render the views in 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.

30) 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

31) What are Non Action methods in MVC?

In 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 
}

32) How to change the action name in 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.

33) 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";
}

34) 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.

35) How we can call a JavaScript function on the change of a Dropdown List in MVC?

Create a JavaScript method:

<script type="text/javascript"> 
function DrpIndexChanged() { }
</script>
Invoke the method:
<%:Html.DropDownListFor(x => x.SelectedProduct, new SelectList(Model.Customers, "Value", "Text"), "Please Select a Customer", new { id = "ddlCustomers", onchange=" DrpIndexChanged ()" })%>

36) 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.

37) Why to use Html.Partial in 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")

38) 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"); }

39) What is RouteConfig.cs in MVC 4?

"RouteConfig.cs" holds the routing configuration for MVC. RouteConfig will be initialized on Application_Start event registered in Global.asax.

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