MVC Interview Questions

MVC - List of Questions

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Reading these MVC interview questions does not mean you will go and clear MVC interviews. The purpose of this article is to quickly brush up your MVC knowledge before you go for MVC interviews. This article does not teach MVC, it’s a last minute revision sheet before going for MVC interviews.

If you want to learn MVC from scratch, start by reading Learn MVC ( Model view controller) step by step 7 days or you can also start with my step by step MVC (Model View Controller) video series from YouTube.

If you want to learn MVC 5 in a short time i.e. 2 days a.k.a 16 hours below is a video series for the same.

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I have tried my level best to cover what questions i have faced in MVC interviews. But i feel the below questions are not enough and in real MVC interview's much more is asked. If you can share your question in the comment below. I would love to incorporate them in this article so that others are benefited.
If your question is great and i like it i will ship you a free copy of my .NET interview question book only in India ( sorry i am not so rich for outside countries).

What is MVC (Model View Controller)?

MVC is an architectural pattern which separates the representation and user interaction. It’s divided into three broader sections, Model, View, and Controller. Below is how each one of them handles the task.

·         The View is responsible for the look and feel.

·         Model represents the real world object and provides data to the View.

·         The Controller is responsible for taking the end user request and loading the appropriate Model and View.

Figure: MVC (Model view controller)

Explain MVC application life cycle?

There are six broader events which occur in MVC application life cycle below diagrams summarize it.

Image Courtesy: - http://www.dotnetinterviewquestions.in/article_explain-mvc-application-life-cycle_210.html

Any web application has two main execution steps first understanding the request and depending on the type of the request sending out appropriate response. MVC application life cycle is not different it has two main phases first creating the request object and second sending our response to the browser.

Creating the request object: -The request object creation has four major steps. Below is the detail explanation of the same.

Step 1 Fill route: - MVC requests are mapped to route tables which in turn specify which controller and action to be invoked. So if the request is the first request the first thing is to fill the route table with routes collection. This filling of route table happens in the global.asax file.

Step 2 Fetch route: - Depending on the URL sent “UrlRoutingModule” searches the route table to create “RouteData” object which has the details of which controller and action to invoke.

Step 3 Request context created: - The “RouteData” object is used to create the “RequestContext” object.

Step 4 Controller instance created: - This request object is sent to “MvcHandler” instance to create the controller class instance. Once the controller class object is created it calls the “Execute” method of the controller class.

Creating Response object: - This phase has two steps executing the action and finally sending the response as a result to the view.

Is MVC suitable for both Windows and Web applications?

The MVC architecture is suited for a web application than Windows. For Window applications, MVP, i.e., “Model View Presenter” is more applicable. If you are using WPF and Silverlight, MVVM is more suitable due to bindings.

What are the benefits of using MVC?

There are two big benefits of MVC:

·         Separation of concerns is achieved as we are moving the code-behind to a separate class file. By moving the binding code to a separate class file we can reuse the code to a great extent.

·         Automated UI testing is possible because now the behind code (UI interaction code) has moved to a simple .NET class. This gives us opportunity to write unit tests and automate manual testing.

Is MVC different from a three layered architecture?

MVC is an evolution of a three layered traditional architecture. Many components of the three layered architecture are part of MVC. So below is how the mapping goes:

Functionality	Three layered / tiered architecture	Model view controller architecture
Look and Feel	User interface	View
UI logic	User interface	Controller
Business logic /validations	Middle layer	Model
Request is first sent to	User interface	Controller
Accessing data	Data access layer	Data Access Layer

Figure: Three layered architecture

What is the latest version of MVC?

MVC 6 is the latest version which is also termed as ASP VNEXT.

What is the difference between each version of MVC 2, 3 , 4, 5 and 6?

MVC 6

ASP.NET MVC and Web API has been merged in to one.

Dependency injection is inbuilt and part of MVC.

Side by side - deploy the runtime and framework with your application

Everything packaged with NuGet, Including the .NET runtime itself.

New JSON based project structure.

No need to recompile for every change. Just hit save and refresh the browser.

Compilation done with the new Roslyn real-time compiler.

vNext is Open Source via the .NET Foundation and is taking public contributions.

vNext (and Rosyln) also runs on Mono, on both Mac and Linux today.

MVC 5

One ASP.NET

Attribute based routing

Asp.Net Identity

Bootstrap in the MVC template

Authentication Filters

Filter overrides

MVC 4

ASP.NET Web API

Refreshed and modernized default project templates

New mobile project template

Many new features to support mobile apps

Enhanced support for asynchronous methods

MVC 3

Razor

Readymade project templates

HTML 5 enabled templates

Support for Multiple View Engines

JavaScript and Ajax

Model Validation Improvements

MVC 2

Client-Side Validation

Templated Helpers

Areas

Asynchronous Controllers

Html.ValidationSummary Helper Method

DefaultValueAttribute in Action-Method Parameters

Binding Binary Data with Model Binders

DataAnnotations Attributes

Model-Validator Providers

New RequireHttpsAttribute Action Filter

Templated Helpers

Display Model-Level Errors

What are HTML helpers in MVC?

HTML helpers help you to render HTML controls in the view. For instance if you want to display a HTML textbox on the view , below is the HTML helper code.

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<%= Html.TextBox("LastName") %>

For checkbox below is the HTML helper code. In this way we have HTML helper methods for every HTML control that exists.

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<%= Html.CheckBox("Married") %>

What is the difference between “HTML.TextBox” vs “HTML.TextBoxFor”?

Both of them provide the same HTML output, “HTML.TextBoxFor” is strongly typed while “HTML.TextBox” isn’t. Below is a simple HTML code which just creates a simple textbox with “CustomerCode” as name.

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Html.TextBox("CustomerCode")

Below is “Html.TextBoxFor” code which creates HTML textbox using the property name ‘CustomerCode” from object “m”.

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Html.TextBoxFor(m => m.CustomerCode)

In the same way we have for other HTML controls like for checkbox we have “Html.CheckBox” and “Html.CheckBoxFor”.

What is routing in MVC?

Routing helps you to define a URL structure and map the URL with the controller.

For instance let’s say we want that when a user types “http://localhost/View/ViewCustomer/”, it goes to the “Customer” Controller and invokes the DisplayCustomer action. This is defined by adding an entry in to theroutes collection using the maproute function. Below is the underlined code which shows how the URL structure and mapping with controller and action is defined.

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routes.MapRoute(

               "View", // Route name

               "View/ViewCustomer/{id}", // URL with parameters

               new { controller = "Customer", action = "DisplayCustomer",

id = UrlParameter.Optional }); // Parameter defaults  

Where is the route mapping code written?

The route mapping code is written in "RouteConfig.cs" file and registered using "global.asax" application start event.

Can we map multiple URL’s to the same action?

Yes, you can, you just need to make two entries with different key names and specify the same controller and action.

Explain attribute based routing in MVC?

This is a feature introduced in MVC 5. By using the "Route" attribute we can define the URL structure. For example in the below code we have decorated the "GotoAbout" action with the route attribute. The route attribute says that the "GotoAbout" can be invoked using the URL structure "Users/about".

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public class HomeController : Controller

{

       [Route("Users/about")]

       public ActionResult GotoAbout()

       {

           return View();

       }

}

What is the advantage of defining route structures in the code?

Most of the time developers code in the action methods. Developers can see the URL structure right upfront rather than going to the “routeconfig.cs” and see the lengthy codes. For instance in the below code the developer can see right upfront that the “GotoAbout” action can be invoked by four different URL structure.

This is much user friendly as compared to scrolling through the “routeconfig.cs” file and going through the length line of code to figure out which URL structure is mapped to which action.

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public class HomeController : Controller

{

       [Route("Users/about")]

       [Route("Users/WhoareWe")]

       [Route("Users/OurTeam")]

       [Route("Users/aboutCompany")]

       public ActionResult GotoAbout()

       {

           return View();

       }

}

How can we navigate from one view to another using a hyperlink?

By using the ActionLink method as shown in the below code. The below code will create a simple URL which helps to navigate to the “Home” controller and invoke the GotoHome action.

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<%= Html.ActionLink("Home","Gotohome") %> 

How can we restrict MVC actions to be invoked only by GET or POST?

We can decorate the MVC action with the HttpGet or HttpPost attribute to restrict the type of HTTP calls. For instance you can see in the below code snippet the DisplayCustomer action can only be invoked by HttpGet. If we try to make HTTP POST on DisplayCustomer, it will throw an error.

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[HttpGet]

public ViewResult DisplayCustomer(int id)

{

    Customer objCustomer = Customers[id];

    return View("DisplayCustomer",objCustomer);

}

How can we maintain sessions in MVC?

Sessions can be maintained in MVC by three ways: tempdata, viewdata, and viewbag.

What is the difference between tempdata, viewdata, and viewbag?

Figure: Difference between tempdata, viewdata, and viewbag

·         Temp data - Helps to maintain data when you move from one controller to another controller or from one action to another action. In other words when you redirect, tempdata helps to maintain data between those redirects. It internally uses session variables.

·         View data - Helps to maintain data when you move from controller to view.

·         View Bag - It’s a dynamic wrapper around view data. When you use Viewbag type, casting is not required. It uses the dynamic keyword internally.

Figure: dynamic keyword

·         Session variables - By using session variables we can maintain data from any entity to any entity.

·         Hidden fields and HTML controls - Helps to maintain data from UI to controller only. So you can send data from HTML controls or hidden fields to the controller using POST or GET HTTP methods.

Below is a summary table which shows the different mechanisms for persistence.

Maintains data between	ViewData/ViewBag	TempData	Hidden fields	Session
Controller to Controller	No	Yes	No	Yes
Controller to View	Yes	No	No	Yes
View to Controller	No	No	Yes	Yes

What is difference between TempData and ViewData ?

“TempData” maintains data for the complete request while “ViewData” maintains data only from Controller to the view.

Does “TempData” preserve data in the next request also?

“TempData” is available through out for the current request and in the subsequent request it’s available depending on whether “TempData” is read or not.

So if “TempData” is once read it will not be available in the subsequent request.

What is the use of Keep and Peek in “TempData”?

Once “TempData” is read in the current request it’s not available in the subsequent request. If we want “TempData” to be read and also available in the subsequent request then after reading we need to call “Keep” method as shown in the code below.

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@TempData[“MyData”];

TempData.Keep(“MyData”);

The more shortcut way of achieving the same is by using “Peek”. This function helps to read as well advices MVC to maintain “TempData” for the subsequent request.

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string str = TempData.Peek("Td").ToString();

If you want to read more in detail you can read from this detailed blog on MVC Peek and Keep.

What are partial views in MVC?

Partial view is a reusable view (like a user control) which can be embedded inside other view. For example let’s say all your pages of your site have a standard structure with left menu, header, and footer as shown in the image below.

Figure: Partial views in MVC

For every page you would like to reuse the left menu, header, and footer controls. So you can go and create partial views for each of these items and then you call that partial view in the main view.

How did you create a partial view and consume it?

When you add a view to your project you need to check the “Create partial view” check box.

Figure: Create partial view

Once the partial view is created you can then call the partial view in the main view using theHtml.RenderPartial method as shown in the below code snippet:

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<body>

<div>

<% Html.RenderPartial("MyView"); %>

</div>

</body>

How can we do validations in MVC?

One of the easiest ways of doing validation in MVC is by using data annotations. Data annotations are nothing but attributes which can be applied on model properties. For example, in the below code snippet we have a simple Customer class with a property customercode.

This CustomerCode property is tagged with a Required data annotation attribute. In other words if this model is not provided customer code, it will not accept it.

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public class Customer

{

    [Required(ErrorMessage="Customer code is required")]

    public string CustomerCode

    {

        set;

        get;

    }

} 

In order to display the validation error message we need to use the ValidateMessageFor method which belongs to the Html helper class.

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<% using (Html.BeginForm("PostCustomer", "Home", FormMethod.Post))

{ %>

<%=Html.TextBoxFor(m => m.CustomerCode)%>

<%=Html.ValidationMessageFor(m => m.CustomerCode)%>

<input type="submit" value="Submit customer data" />

<%}%>

Later in the controller we can check if the model is proper or not by using the ModelState.IsValid property and accordingly we can take actions.

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public ActionResult PostCustomer(Customer obj)

{

    if (ModelState.IsValid)

    {

        obj.Save();

        return View("Thanks");

    }

    else

    {

        return View("Customer");

    }

}

Below is a simple view of how the error message is displayed on the view.

Figure: Validations in MVC

Can we display all errors in one go?

Yes, we can; use the ValidationSummary method from the Html helper class.

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<%= Html.ValidationSummary() %>  

What are the other data annotation attributes for validation in MVC?

If you want to check string length, you can use StringLength.

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[StringLength(160)]

public string FirstName { get; set; }

In case you want to use a regular expression, you can use the RegularExpression attribute.

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[RegularExpression(@"[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}")]public string Email { get; set; }

If you want to check whether the numbers are in range, you can use the Range attribute.

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[Range(10,25)]public int Age { get; set; }

Sometimes you would like to compare the value of one field with another field, we can use the Compareattribute.

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public string Password { get; set; }[Compare("Password")]public string ConfirmPass { get; set; }

In case you want to get a particular error message , you can use the Errors collection.

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var ErrMessage = ModelState["Email"].Errors[0].ErrorMessage;

If you have created the model object yourself you can explicitly call TryUpdateModel in your controller to check if the object is valid or not.

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TryUpdateModel(NewCustomer);

In case you want add errors in the controller you can use the AddModelError function.

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ModelState.AddModelError("FirstName", "This is my server-side error.");

How can we enable data annotation validation on client side?

It’s a two-step process: first reference the necessary jQuery files.

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The second step is to call the EnableClientValidation method.

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<% Html.EnableClientValidation(); %>

What is Razor in MVC?

It’s a light weight view engine. Till MVC we had only one view type, i.e., ASPX. Razor was introduced in MVC 3.

Why Razor when we already have ASPX?

Razor is clean, lightweight, and syntaxes are easy as compared to ASPX. For example, in ASPX to display simple time, we need to write:

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<%=DateTime.Now%>

In Razor, it’s just one line of code:

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@DateTime.Now

So which is a better fit, Razor or ASPX?

As per Microsoft, Razor is more preferred because it’s light weight and has simple syntaxes.

How can you do authentication and authorization in MVC?

You can use Windows or Forms authentication for MVC.

How to implement Windows authentication for MVC?

For Windows authentication you need to modify the web.config file and set the authentication mode to Windows.

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<authentication mode="Windows"/>

<authorization>

<deny users="?"/>

</authorization>

Then in the controller or on the action, you can use the Authorize attribute which specifies which users have access to these controllers and actions. Below is the code snippet for that. Now only the users specified in the controller and action can access it.

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[Authorize(Users= @"WIN-3LI600MWLQN\Administrator")]

public class StartController : Controller

{

    //

    // GET: /Start/

    [Authorize(Users = @"WIN-3LI600MWLQN\Administrator")]

    public ActionResult Index()

    {

        return View("MyView");

    }

}

How do you implement Forms authentication in MVC?

Forms authentication is implemented the same way as in ASP.NET. The first step is to set the authentication mode equal to Forms. The loginUrl points to a controller here rather than a page.

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<authentication mode="Forms">

<forms loginUrl="~/Home/Login"  timeout="2880"/>

</authentication>

We also need to create a controller where we will check if the user is proper or not. If the user is proper we will set the cookie value.

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public ActionResult Login()

{

    if ((Request.Form["txtUserName"] == "Shiv") &&

          (Request.Form["txtPassword"] == "Shiv@123"))

    {

        FormsAuthentication.SetAuthCookie("Shiv",true);

        return View("About");

    }

    else

    {

        return View("Index");

    }

}

All the other actions need to be attributed with the Authorize attribute so that any unauthorized user making a call to these controllers will be redirected to the controller (in this case the controller is “Login”) which will do the authentication.

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[Authorize]

PublicActionResult Default()

{

return View();

}

[Authorize]

publicActionResult About()

{

return View();

}

How to implement AJAX in MVC?

You can implement AJAX in two ways in MVC:

·         AJAX libraries

·         jQuery

Below is a simple sample of how to implement AJAX by using the “AJAX” helper library. In the below code you can see we have a simple form which is created by using the Ajax.BeginForm syntax. This form calls a controller action called getCustomer. So now the submit action click will be an asynchronous AJAX call.

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"/Action1" method=post>

"/Action2" method=post>

Please do read this blog which has detailed steps of how model binders can be created using “IModelBinder” interface: - Explain MVC model Binders?