What is the difference between ViewBag and ViewData in 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 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 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 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.
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.
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Explain JSON Binding?
JavaScript Object Notation (JSON) binding support started from MVC3 onwards via the new JsonValueProviderFactory, which allows the action methods to accept and model-bind data in JSON format. This is useful in Ajax scenarios like client templates and data binding that need to post data back to the server.
Explain Dependency Resolution?
Dependency Resolver again has been introduced in MVC3 and it is greatly simplified the use of dependency injection in your applications. This turn to be easier and useful for decoupling the application components and making them easier to test and more configurable.
Explain Bundle.Config in MVC5?
“BundleConfig.cs” in MVC5 is used to register the bundles by the bundling and minification system. Many bundles are added by default including jQuery libraries like — jquery.validate, Modernizr, and default CSS references.
How route table has been created in ASP.NET MVC?
Method — “RegisterRoutes()” is used for registering the routes which will be added in “Application_Start()” method of global.asax file, which is fired when the application is loaded or started.
Which are the important namespaces used in MVC?
Below are the important namespaces used in MVC -
System.Web.Mvc
System.Web.Mvc.Ajax
System.Web.Mvc.Html
System.Web.Mvc.Async
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.
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.
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)
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.
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 ()” })%>
What is the meaning of Unobtrusive JavaScript?
This is a general term that conveys a general philosophy, similar to the term REST (Representational State Transfer). Unobtrusive JavaScript doesn’t intermix 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 ViewModel in MVC?
ViewModel is a plain class with properties, which is used to bind it to strongly typed view. ViewModel can have the validation rules defined for its properties using data annotations.
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 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”)
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.
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.
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.
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
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