Dotnet Blogger: ASP.NET MVC INTERVIEW QUESTIONS PART-1

1) What is MVC?

MVC is a pattern which is used to split the application's implementation logic into three components: models, views, and controllers.

2) Can you explain Model, Controller and View in MVC?

Model – It’s a business entity and it is used to represent the application data.

Controller – Request sent by the user always scatters through controller and its responsibility is to redirect to the specific view using View () method.

View – It’s the presentation layer of MVC.

3) Explain the new features added in version 4 of MVC (MVC4)?

Following are features added newly –

· Mobile templates

· Added ASP.NET Web API template for creating REST based services.

· Asynchronous controller task support.

· Bundling the java scripts.

· Segregating the configs for MVC routing, Web API, Bundle etc.

4) Can you explain the page life cycle of MVC?

Below are the processed followed in the sequence -

· App initialization

· Routing

· Instantiate and execute controller

· Locate and invoke controller action

· Instantiate and render view.

5) What are the advantages of 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.

6) What is Separation of Concerns in ASP.NET MVC?

It’s is the process of breaking the program into various distinct features which overlaps in functionality as little as possible. MVC pattern concerns on separating the content from presentation and data-processing from content.

7) What is Razor View Engine?

Razor is the first major update to render HTML in 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 MvcMusicStore.Models.Customer

@{ViewBag.Title = "Get Customers";}

<div class="cust"> <h3><em>@Model.CustomerName</em> </h3>

8) 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.

9) What is the use of View Model in 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.

10) What you mean by Routing in 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.

11) What are Actions in 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.

12) What is Attribute Routing in MVC?

ASP.NET Web API supports this type routing. This is introduced in MVC5. In this type of routing, attributes are being used to define the routes. This type of routing gives more control over classic URI Routing. Attribute Routing can be defined at controller level or at Action level like –

[Route (“{action = TestCategoryList}”)] - Controller Level

[Route (“customers/{TestCategoryId:int:min(10)}”)] - Action Level

13) How to enable Attribute Routing?

Just add the method – “MapMvcAttributeRoutes()” to enable attribute routing as shown below

Public static void RegistearRoutes(RouteCollection routes)

{

routes.IgnoareRoute("{resource}.axd/{*pathInfo}");

//enabling attribute routing

routes.MapMvcAttributeRoutes();

//convention-based routing

routes.MapRoute

(

name: "Default",

url: "{controller}/{action}/{id}",

defaults: new { controller = "Customer", action = "GetCustomerList", id = UrlParameter.Optional }

);

}

14) Explain JSON Binding?

JavaScript Object Notation (JSON) binding support started from MVC3 onwards via the new Json Value Provider Factory, 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.

15) 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.

16) Explain Bundle.Config in MVC4?

"BundleConfig.cs" in MVC4 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.

17) 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.

18) 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

19) What is View Data?

View data contains the key, value pairs as dictionary and this is derived from class – “ViewDataDictionary“. In action method we are setting the value for view data and in view the value will be fetched by typecasting.

20) What is the difference between View Bag and View Data in MVC?

View Bag is a wrapper around View Data, which allows creating dynamic properties. Advantage of view bag over view data will be –

· In View Bag no need to typecast the objects as in View Data.

· View Bag will take advantage of dynamic keyword which is introduced in version 4.0. But before using View Bag we have to keep in mind that View Bag is slower than View Data.

21) Explain TempData in MVC?

TempData is again a key, value pair as View Data. 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 –

1. Url – This is the request URL.

2. Confirm – This is used to specify the message which is to be displayed in confirm box.

3. OnBegin – Javascript method name to be given here and this will be called before the AJAX request.

4. OnComplete – Javascript method name to be given here and this will be called at the end of AJAX request.

5. OnSuccess - Javascript method name to be given here and this will be called when AJAX request is successful.

6. OnFailure - Javascript method name to be given here and this will be called when AJAX request is failed.

7. 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 its master page.

26) Explain Sections is MVC?

Sections 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:

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.

40) What are Scaffold templates in MVC?

Scaffolding in ASP.NET MVC is used to generate the Controllers, Model and Views for create, read, update, and delete (CRUD) functionality in an application. The scaffolding will be knowing the naming conventions used for models and controllers and views.

41) Explain the types of Scaffoldings.

Below are the types of scaffoldings –

· Empty

· Create

· Delete

· Details

· Edit

· List

42) Can a view be shared across multiple controllers? If Yes, How we can do that?

Yes, we can share a view across multiple controllers. We can put the view in the “Shared” folder. When we create a new MVC Project we can see the Layout page will be added in the shared folder, which is because it is used by multiple child pages.

43) What are the components required to create a route in MVC?

· Name - This is the name of the route.

· URL Pattern – Placeholders will be given to match the request URL pattern.

· Defaults –When loading the application which controller, action to be loaded along with the parameter.

44) Why to use “{resource}.axd/{*pathInfo}” in routing in MVC?

Using this default route - {resource}.axd/{*pathInfo}, we can prevent the requests for the web resources files like - WebResource.axd or ScriptResource.axd from passing to a controller.

45) Can we add constraints to the route? If yes, explain how we can do it?

Yes we can add constraints to route in following ways –

· Using Regular Expressions

· Using object which implements interface - IRouteConstraint.

46) What are the possible Razor view extensions?

Below are the two types of extensions razor view can have –

· .cshtml – In C# programming language this extension will be used.

· .vbhtml - In VB programming language this extension will be used.

47) What is Partial View in MVC?

Partial View is similar to User Controls 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()

48) How we can add the CSS in MVC?

Below is the sample code snippet to add css to razor views –

49) Can I add MVC Test cases in Visual Studio Express?

No. We cannot add the test cases in Visual Studio Express edition it can be added only in Professional and Ultimate versions of Visual Studio.

50) What is the use .Glimpse in MVC?

Glimpse is an open source tool for debugging the routes in MVC. It is the client side debugger. Glimpse has to be turned on by visiting to local url link -

· http://localhost:portname//glimpse.axd

This is a popular and useful tool for debugging which tracks the speed details, url details etc.

51) What is the need of Action Filters in MVC?

Action Filters allow us to execute the code before or after action has been executed. This can be done by decorating the action methods of controls with MVC attributes.

52) Mention some action filters which are used regularly in MVC?

Below is some action filters used –

· Authentication

· Authorization

· HandleError

· OutputCache

53) How can we determine action invoked from HTTP GET or HTTP POST?

This can be done in following way –

·Use class – “HttpRequestBase” and use the method – “HttpMethod” to determine the action request type.

54) In Server how to check whether model has error or not in MVC?

Whenever validation fails it will be tracked in ModelState. By using property – IsValid it can be determined. In Server code, checks like this –

if(ModelState.IsValid)

{

// No Validation Errors

}

55) How to make sure Client Validation is enabled in MVC?

In Web.Config there are tags called – “ClientValidationEnabled” and “UnobtrusiveJavaScriptEnabled”. We can set the client side validation just by setting these two tags “true”, then this setting will be applied at the application level.

56) What are Model Binders in MVC?

For Model Binding we will use class called – “ModelBinders”, which gives access to all the model binders in an application. We can create a custom model binder by inheriting “IModelBinder”.

57) How we can handle the exception at controller level in MVC?

Exception Handling is made simple in MVC and it can be done by just overriding “OnException” and set the result property of the filtercontext object (as shown below) to the view detail, which is to be returned in case of exception.

Protected overrides void OnException(ExceptionContext filterContext)

{

}

58) Does Tempdata hold the data for other request in MVC?

If Tempdata is assigned in the current request then it will be available for the current request and the subsequent request and it depends whether data in TempData read or not. If data in Tempdata is read then it would not be available for the subsequent requests.

59) Explain Keep method in Tempdata in MVC?

As explained above in case data in Tempdata has been read in current request only then “Keep” method has been used to make it available for the subsequent request.

@TempData[“TestData”];
TempData.Keep(“TestData”);

60) Explain Peek method in Tempdata in MVC?

Similar to keep method we have one more method called “Peek” which is used for the same purpose. This method used to read data in Tempdata and it maintains the data for subsequent request.

String A4str = TempData.Peek("TT").ToString();

61) What is Area in MVC?

Area is used to store the details of the modules of our project. This is really helpful for big applications, where controllers, views and models are all in main controller, view and model folders and it is very difficult to manage.

62) How we can register the Area in MVC?

When we have created an area make sure this will be registered in “Application_Start” event in Global.asax. Below is the code snippet where area registration is done –

Protected void Application_Start()

{

AreaRegistration.RegisterAllAreas();

}

63) What are child actions in MVC?

To create reusable widgets child actions are used and this will be embedded into the parent views. In MVC Partial views are used to have reusability in the application. Child action mainly returns the partial views.

64) How we can invoke child actions in MVC?

“ChildActionOnly” attribute is decorated over action methods to indicate that action method is a child action. Below is the code snippet used to denote the child action –

[ChildActionOnly]

Public ActionResultMenuBar()

{

//Logic here

Return PartialView();

}

65) What is Dependency Injection in MVC?

It’s a design pattern and is used for developing loosely couple code. This is greatly used in the software projects. This will reduce the coding in case of changes on project design so this is vastly used.

66) Explain the advantages of Dependency Injection (DI) in MVC?

Below are the advantages of DI –

· Reduces class coupling

· Increases code reusing

· Improves code maintainability

· Improves application testing

67) Explain Test Driven Development (TDD)?

TDD is a methodology which says; write your tests first before you write your code. In TDD, tests drive your application design and development cycles. You do not do the check-in of your code into source control until your entire unit tests pass.

68) Explain the tools used for unit testing in MVC?

Below are the tools used for unit testing –

· NUnit

· xUnit.NET

· Ninject 2

· Moq

69) What is Representational State Transfer (REST) mean?

REST is an architectural style which uses HTTP protocol methods like GET, POST, PUT, and DELETE to access the data. MVC works in this style. In MVC 4 there is a support for Web API which uses to build the service using HTTP verbs.

70) How to use Jquery Plugins in MVC validation?

We can use data-annotations for validation in MVC. If we want to use validation during runtime using Jquery then we can use Jquery plugins for validation.

Eg: If validation is to be done on customer name textbox then we can do as –

$('#CustomerName').rules("add",

{

Required: true,

Minlength: 2,

Messages: {

Required: “please enter name”,

Minlength: "Minimum length is 2”

}

});

71) How we can multiple submit buttons in MVC?

Below are the scenario and the solution to solve multiple submit buttons issue.

Scenario –

{

@using(Html.BeginForm(“MyTestAction”,”MyTestController”)

}

Solution:

Public ActionResult MyTestAction(string submit) //submit will have value either “MySave” or “MyEdit”

{

// Write code here

}

72) What are the differences between Partial View and Display Template and Edit Templates in MVC?

Display Templates – These are model centric. Meaning it depends on the properties of the view model used. It uses convention that will only display like divs or labels.

Edit Templates – These are also model centric but will have editable controls like Textboxes.

Partial View – These are view centric. These will differ from templates by the way they render the properties (Id’s) Eg : CategoryViewModel has Product class property then it will be rendered as Model.Product.ProductName but in case of templates if we CategoryViewModel has List<Product> then @Html.DisplayFor(m => m.Products) works and it renders the template for each item of this list.

73) Can I set the unlimited length for “maxJsonLength” property in config?

No. We can’t set unlimited length for property maxJsonLength. Default value is - 102400 and maximum value what we can set would be – 2147483644.

74) Can I use Razor code in Javascript in MVC?

Yes. We can use the razor code in javascript in cshtml by using <text> element.

@foreach (var item in Model)

{
<text>
//javascript goes here which uses the server value

</text>
}
</script>

75) How can I return string result from Action in MVC?

Below is the code snippet to return string from action method –

Public ActionResult Test Action ()

{

Return Content (“Hello Test!!”);

}

76) How to return the JSON from action method in MVC?

Below is the code snippet to return string from action method –

Public ActionResult TestAction()

{

Return JSON(new { prop1 = “Test1”, prop2 = “Test2” })

}

77) How we can override the action names in MVC?

If we want to override the action names we can do like this –

[ActionName("NewActionName")]

Public ActionResult TestAction()

{

Return View();

}

78) In which assembly is the MVC framework defined?

System.Web.Mvc

79) Is it possible to combine ASP.NET web forms and ASP.MVC and develop a single web application?

Yes, it is possible to combine ASP.NET web forms and ASP.MVC and develop a single web application.

80) What do Model, View and Controller represent in an MVC application?

Model: Model represents the application data domain. In short the applications business logic is contained within the model.

View: Views represent the user interface, with which the end users interact. In short the all the user interface logic is contained within the UI.

Controller: Controller is the component that responds to user actions. Based on the user actions, the respective controller, work with the model, and selects a view to render that displays the user interface. The user input logic is contained within the controller.

81) What is the greatest advantage of using asp.net mvc over asp.net web forms?

It is difficult to unit test UI with web forms, where views in mvc can be very easily unit tested.

82) Which approach provides better support for test driven development - ASP.NET MVC or ASP.NET Web forms?

ASP.NET MVC

83) What are the advantages of ASP.NET MVC?

1. Extensive support for TDD. With asp.net MVC, views can also be very easily unit tested.

2. Complex applications can be easily managed

3. Separation of concerns. Different aspects of the application can be divided into Model, View and Controller.

4. ASP.NET MVC views are light weight, as they do not use view state.

84) Is it possible to unit test an MVC application without running the controllers in an ASP.NET process?

Yes, all the features in an asp.net MVC application are interface based and hence mocking is much easier. So, we don't have to run the controllers in an ASP.NET process for unit testing.

85) Is it possible to share a view across multiple controllers?

Yes, put the view into the shared folder. This will automatically make the view available across multiple controllers.

86) What is the role of a controller in an MVC application?

The controller responds to user interactions, with the application, by selecting the action method to execute and else selecting the view to render.

87) Where the routing rules are defined in an asp.net MVC application?

In Application_Start event in Global.asax

88) Name a few different return types of a controller action method?

The following are just a few return types of a controller action method. In general an action method can return an instance of a any class that derives from Action Result class.

1. View Result

2. JavaScript Result

3. Redirect Result

4. Content Result

5. Json Result

89) What is the significance of NonActionAttribute?

In general, all public methods of a controller class are treated as action methods. If you want prevent this default behavior, just decorate the public method with NonActionAttribute.

90) What is the significance of ASP.NET routing?

ASP.NET MVC uses ASP.NET routing, to map incoming browser requests to controller action methods. ASP.NET Routing makes use of route table. Route table is created when your web application first starts. The route table is present in the Global.asax file.

91) What are the 3 segments of the default route that is present in an ASP.NET MVC application?

1st Segment - Controller Name

2nd Segment - Action Method Name

3rd Segment - Parameter that is passed to the action method

Example: http://pragimtech.com/Customer/Details/5

Controller Name = Customer

Action Method Name = Details

Parameter Id = 5

92) ASP.NET MVC application makes use of settings at 2 places for routing to work correctly. What are these 2 places?

1. Web.Config File: ASP.NET routing has to be enabled here.

2. Global.asax File: The Route table is created in the application Start event handler, of the Global.asax file.

93) What is the advantage of using ASP.NET routing?

In an ASP.NET web application that does not make use of routing, an incoming browser request should map to a physical file. If the file does not exist, we get page not found error.

An ASP.NET web application that does make use of routing makes use of URLs that do not have to map to specific files in a Web site. Because the URL does not have to map to a file, you can use URLs that are descriptive of the user's action and therefore are more easily understood by users.

94) What are the 3 things that are needed to specify a route?

1. URL Pattern - You can include placeholders in a URL pattern so that variable data can be passed to the request handler without requiring a query string.

2. Handler - The handler can be a physical file such as an .aspx file or a controller class.

3. Name for the Route - Name is optional.

95) Is the following route definition a valid route definition?

{Controller}{Action}/ {id}

No, the above definition is not a valid route definition, because there is no literal value or delimiter between the placeholders. Therefore, routing cannot determine where to separate the value for the controller placeholder from the value for the action placeholder.

96) What is the use of the following default route?

{Resource}.axd/ {*pathInfo}

This route definition, prevent requests for the Web resource files such as WebResource.axd or ScriptResource.axd from being passed to a controller.

97) What is the difference between adding routes, to a webforms application and to an mvc application?

To add routes to a web forms application, we use MapPageRoute() method of the RouteCollection class, where as to add routes to an MVC application we use MapRoute() method.

98) How do you handle variable number of segments in a route definition?

Use a route with a catch-all parameter. An example is shown below. * is referred to as catch-all parameter.

Controller/ {action}/ {*parameter values}

99) What are the 2 ways of adding constraints to a route?

1. Use regular expressions

2. Use an object that implements IRouteConstraint interface.

100) Give 2 examples for scenarios when routing is not applied?

1. A Physical File is found that Matches the URL Pattern - This default behavior can be overridden by setting the Route Existing Files property of the Route Collection object to true.

2. Routing Is Explicitly Disabled for a URL Pattern - Use the RouteCollection.Ignore () method to prevent routing from handling certain requests.

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Friday, 22 December 2017

ASP.NET MVC INTERVIEW QUESTIONS PART-1

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