ASP.net MVC Interview Questions (1)

ASP.NET MVC Interview Questions

1) 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)

2) Explain MVC application life cycle?

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

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.

3) 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.

4) 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.

5) 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

6) What is the latest version of MVC?

When this notes was written, five versions were released of MVC: MVC 1 , MVC 2, MVC 3,MVC 4 and MVC 5. So the latest is MVC 5.

7) What is the difference between each version of MVC?

Below is a detailed table of differences. But during an interview it’s difficult to talk about all of them due to time limitation. So I have highlighted the important differences that you can run through before the interviewer.

MVC 2 MVC 3 MVC 4

Client-side validation Templated Helpers

Razor Readymade

ASP.NET Web API

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

project templates

HTML 5 enabled templates

Support for Multiple View Engines, JavaScript, and AJAX

Model Validation Improvements

Refreshed and modernized default project templates. New mobile project template.

Many new features to support mobile apps

Enhanced support for asynchronous methods

8) 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.

@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.

@Html.CheckBox("Married")

9) 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.

@Html.TextBox("CustomerCode")

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

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”.

10) 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 the routes collection using the maproute function. Below is the underlined code which shows how the URL structure and mapping with controller and action is defined.

routes.MapRoute( "View", // Route name "View/ViewCustomer/{id}", // URL with parameters new { controller = "Customer", action = "DisplayCustomer", id = UrlParameter.Optional }); // Parameter defaults

11) Where is the route mapping code written?

The route mapping code is written in the “global.asax” file or “RouteConfig.cs” file.

12) 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.

13) 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.

@Html.ActionLink("Home","Go to home")

14) 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.

[HttpGet] public ViewResult DisplayCustomer(int id) { Customer objCustomer = Customers[id]; return View("DisplayCustomer",objCustomer); }

15) How can we pass data from controller to view?

There are three ways: tempdata, viewdata, and viewbag.

16) 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

17) 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.

18) 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 the Html.RenderPartial method as shown in the below code snippet:

<body> <div> @{ @Html.RenderPartial("MyView"); } </div> </body>

19) 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.

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.

@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.

public ActionResult PostCustomer(Customer obj) {

if (ModelState.IsValid) { obj.Save(); return View("Thanks"); } else { return View("Customer"); } }

20) Can we display all errors in one go?

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

@Html.ValidationSummary()

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

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

[StringLength(160)] public string FirstName { get; set; }

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

[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.

[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 Compare attribute.

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.

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.

TryUpdateModel(NewCustomer);

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

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

21) How can we enable data annotation validation on client side?

Reference the necessary jQuery files.

<script src="@Url.Content("~/Scripts/jquery-1.5.1.js")" type="text/javascript"></script>

You can use Windows or Forms authentication for MVC.

26) 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.

<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.

[Authorize(Users= @"WIN-3LI600MWLQN\Administrator")] public class StartController : Controller { // // GET: /Start/ [Authorize(Users = @"WIN-3LI600MWLQN\Administrator")] public ActionResult Index() { return View("MyView"); } }

27) 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.

<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.

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.

[Authorize] PublicActionResult Default() { return View();

} [Authorize] publicActionResult About() { return View(); }

28) 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.

<script language="javascript"> function OnSuccess(data1) { // Do something here } </script> <div> <% var AjaxOpt = new AjaxOptions{OnSuccess="OnSuccess"}; %> <% using (Ajax.BeginForm("getCustomer","MyAjax",AjaxOpt)) { %> <input id="txtCustomerCode" type="text" /><br /> <input id="txtCustomerName" type="text" /><br />

<input id="Submit2" type="submit" value="submit"/></div> <%} %>

In case you want to make AJAX calls on hyperlink clicks, you can use the Ajax.ActionLink function as shown in the below code.

Figure: Implement AJAX in MVC

So if you want to create an AJAX asynchronous hyperlink by name GetDate which calls the GetDate function in the controller, below is the code for that. Once the controller responds, this data is displayed in the HTML DIV tag named DateDiv.

<span id="DateDiv" /> <%: Ajax.ActionLink("Get Date","GetDate", new AjaxOptions {UpdateTargetId = "DateDiv" }) %>

Below is the controller code. You can see how the GetDate function has a pause of 10 seconds.

public class Default1Controller : Controller { public string GetDate() {

Thread.Sleep(10000); return DateTime.Now.ToString(); } }

The second way of making an AJAX call in MVC is by using jQuery. In the below code you can see we are making an AJAX POST call to a URL /MyAjax/getCustomer. This is done by using $.post. All this logic is put into a function called GetData and you can make a call to the GetData function on a button or a hyperlink click event as you want.

function GetData() { var url = "/MyAjax/getCustomer"; $.post(url, function (data) { $("#txtCustomerCode").val(data.CustomerCode); $("#txtCustomerName").val(data.CustomerName); } ) }

29) What kind of events can be tracked in AJAX?

Figure: Tracked in AJAX

30) What is the difference between ActionResult and ViewResult?

ActionResult is an abstract class while ViewResult derives from the ActionResult class. ActionResult has several derived classes like ViewResult, JsonResult, FileStreamResult, and so on.

ActionResult can be used to exploit polymorphism and dynamism. So if you are returning different types of views dynamically, ActionResult is the best thing. For example in the below code snippet, you can see we have a simple action called DynamicView. Depending on the flag (IsHtmlView) it will either return a ViewResult or JsonResult.

public ActionResult DynamicView() { if (IsHtmlView) return View(); // returns simple ViewResult else return Json(); // returns JsonResult view }

31) What are the different types of results in MVC?

Note: It’s difficult to remember all the 11 types. But some important ones you can remember for the interview are ActionResult, ViewResult, and JsonResult. Below is a detailed list for your interest:

There 11 kinds of results in MVC, at the top is the ActionResult class which is a base class that can have 11 subtypes as listed below:

1. ViewResult - Renders a specified view to the response stream

2. PartialViewResult - Renders a specified partial view to the response stream

3. EmptyResult - An empty response is returned 4. RedirectResult - Performs an HTTP redirection to a specified URL 5. RedirectToRouteResult - Performs an HTTP redirection to a URL

that is determined by the routing engine, based on given route data

6. JsonResult - Serializes a given ViewData object to JSON format 7. JavaScriptResult - Returns a piece of JavaScript code that can be

executed on the client 8. ContentResult - Writes content to the response stream without

requiring a view 9. FileContentResult - Returns a file to the client 10. FileStreamResult - Returns a file to the client, which is

provided by a Stream 11. FilePathResult - Returns a file to the client

32) What are ActionFilters in MVC?

ActionFilters help you to perform logic while an MVC action is executing or after an MVC action has executed.

Figure: ActionFilters in MVC

Action filters are useful in the following scenarios:

1. Implement post-processing logic before the action happens. 2. Cancel a current execution. 3. Inspect the returned value. 4. Provide extra data to the action.

You can create action filters by two ways:

Inline action filter. Creating an ActionFilter attribute.

To create an inline action attribute we need to implement the IActionFilter interface. The IActionFilter interface has two methods: OnActionExecuted and OnActionExecuting. We can implement pre-processing logic or cancellation logic in these methods.

public class Default1Controller : Controller , IActionFilter { public ActionResult Index(Customer obj) { return View(obj); } void IActionFilter.OnActionExecuted(ActionExecutedContext filterContext) { Trace.WriteLine("Action Executed"); } void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext) { Trace.WriteLine("Action is executing");

} }

The problem with the inline action attribute is that it cannot be reused across controllers. So we can convert the inline action filter to an action filter attribute. To create an action filter attribute we need to inherit from ActionFilterAttribute and implement the IActionFilter interface as shown in the below code.

public class MyActionAttribute : ActionFilterAttribute , IActionFilter { void IActionFilter.OnActionExecuted(ActionExecutedContext filterContext) { Trace.WriteLine("Action Executed"); } void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext) { Trace.WriteLine("Action executing"); } }

Later we can decorate the controllers on which we want the action attribute to execute. You can see in the below code I have decorated the Default1Controller with the MyActionAttribute class which was created in the previous code.

[MyActionAttribute] public class Default1Controller : Controller { public ActionResult Index(Customer obj) { return View(obj);

} }

33) Can we create our custom view engine using MVC?

Yes, we can create our own custom view engine in MVC. To create our own custom view engine we need to follow three steps:

Let’ say we want to create a custom view engine where in the user can type a command like “<DateTime>” and it should display the current date and time.

Step 1: We need to create a class which implements the IView interface. In this class we should write the logic of how the view will be rendered in the render function. Below is a simple code snippet for that.

public class MyCustomView : IView { private string _FolderPath; // Define where our views are stored public string FolderPath { get { return _FolderPath; } set { _FolderPath = value; } } public void Render(ViewContext viewContext, System.IO.TextWriter writer) { // Parsing logic <dateTime> // read the view file string strFileData = File.ReadAllText(_FolderPath);

// we need to and replace <datetime> datetime.now value string strFinal = strFileData.Replace("<DateTime>", DateTime.Now.ToString()); // this replaced data has to sent for display writer.Write(strFinal); } }

Step 2: We need to create a class which inherits from VirtualPathProviderViewEngine and in this class we need to provide the folder path and the extension of the view name. For instance, for Razor the extension is “cshtml”; for aspx, the view extension is “.aspx”, so in the same way for our custom view, we need to provide an extension. Below is how the code looks like. You can see the ViewLocationFormats is set to the Views folder and the extension is “.myview”.

public class MyViewEngineProvider : VirtualPathProviderViewEngine { // We will create the object of Mycustome view public MyViewEngineProvider() // constructor { // Define the location of the View file this.ViewLocationFormats = new string[] { "~/Views/{1}/{0}.myview", "~/Views/Shared/{0}.myview" }; //location and extension of our views } protected override IView CreateView( ControllerContext controllerContext, string viewPath, string masterPath) {

var physicalpath = controllerContext.HttpContext.Server.MapPath(viewPath); MyCustomView obj = new MyCustomView(); // Custom view engine class obj.FolderPath = physicalpath; // set the path where the views will be stored return obj; // returned this view paresing // logic so that it can be registered in the view engine collection } protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath) { var physicalpath = controllerContext.HttpContext.Server.MapPath(partialPath); MyCustomView obj = new MyCustomView(); // Custom view engine class obj.FolderPath = physicalpath; // set the path where the views will be stored return obj; // returned this view paresing logic // so that it can be registered in the view engine collection } }

Step 3: We need to register the view in the custom view collection. The best place to register the custom view engine in the ViewEngines collection is the global.asax file. Below is the code snippet for that.

protected void Application_Start() { // Step3 :- register this object in the view engine collection ViewEngines.Engines.Add(new MyViewEngineProvider()); …..

}

Below is a simple output of the custom view written using the commands defined at the top.

Figure: Custom view engine using MVC

If you invoke this view, you should see the following output:

34) How to send result back in JSON format in MVC

In MVC, we have the JsonResult class by which we can return back data in JSON format. Below is a simple sample code which returns back a Customer object in JSON format using JsonResult.

public JsonResult getCustomer() { Customer obj = new Customer(); obj.CustomerCode = "1001"; obj.CustomerName = "Shiv"; return Json(obj,JsonRequestBehavior.AllowGet); }

Below is the JSON output of the above code if you invoke the action via the browser.

35) What is WebAPI?

HTTP is the most used protocol. For the past many years, browser was the most preferred client by which we consumed data exposed over HTTP. But as years passed by, client variety started spreading out. We had demand to consume data on HTTP from clients like mobile, JavaScript, Windows applications, etc.

For satisfying the broad range of clients REST was the proposed approach. You can read more about REST from the WCF chapter.

WebAPI is the technology by which you can expose data over HTTP following REST principles.

36) But WCF SOAP also does the same thing, so how does WebAPI differ?

SOAP WEB API Size Heavy weight because of

complicated WSDL structure.

Light weight, only the necessary information is transferred.

Protocol Independent of protocols. Only for HTTP protocol Formats To parse SOAP message, the

client needs to understand WSDL format. Writing custom code for parsing WSDL is a heavy duty task. If your client is smart enough to create proxy objects like

Output of WebAPI are simple string messages, JSON, simple XML format, etc. So writing parsing logic for that is very easy.

how we have in .NET (add reference) then SOAP is easier to consume and call.

Principles SOAP follows WS-* specification.

WebAPI follows REST principles. (Please refer to REST in WCF chapter.)

37) With WCF you can implement REST, so why WebAPI?

WCF was brought into implement SOA, the intention was never to implement REST. WebAPI is built from scratch and the only goal is to create HTTP services using REST. Due to the one point focus for creating REST service, WebAPI is more preferred.

38) How to implement WebAPI in MVC

Below are the steps to implement WebAPI:

Step 1: Create the project using the WebAPI template.

Figure: Implement WebAPI in MVC

Step 2: Once you have created the project you will notice that the controller now inherits from ApiController and you can now implement POST, GET, PUT, and DELETE methods of the HTTP protocol.

public class ValuesController : ApiController { // GET api/values public IEnumerable<string> Get() { return new string[] { "value1", "value2" }; } // GET api/values/5 public string Get(int id) { return "value"; } // POST api/values public void Post([FromBody]string value) { } // PUT api/values/5 public void Put(int id, [FromBody]string value) { } // DELETE api/values/5 public void Delete(int id) { } }

Step 3: If you make an HTTP GET call you should get the below results:

Figure: HTTP

39) How can we detect that an MVC controller is called by POST or GET?

To detect if the call on the controller is a POST action or a GET action we can use the Request.HttpMethod property as shown in the below code snippet.

public ActionResult SomeAction() { if (Request.HttpMethod == "POST") { return View("SomePage"); } else { return View("SomeOtherPage"); } }

40) What is bundling and minification in MVC?

Bundling and minification helps us improve request load times of a page thus increasing performance.

41) How does bundling increase performance?

Web projects always need CSS and script files. Bundling helps us combine multiple JavaScript and CSS files in to a single entity thus minimizing multiple requests in to a single request.

For example consider the below web request to a page . This page consumes two JavaScript files Javascript1.js and Javascript2.js. So when this is page is requested it makes three request calls:

One for the Index page. Two requests for the other two JavaScript files: Javascript1.js and

Javascript2.js.

The below scenario can become worse if we have a lot of JavaScript files resulting in multiple requests, thus decreasing performance. If we can somehow combine all the JS files into a single bundle and request them as a single unit that would result in increased performance (see the next figure which has a single request).

So how do we implement bundling in MVC?

Open BundleConfig.cs from the App_Start folder.

In BundleConfig.cs, add the JS files you want bundle into a single entity in to the bundles collection. In the below code we are combining all the javascript JS files which exist in the Scripts folder as a single unit in to the bundle collection.

bundles.Add(new ScriptBundle("~/Scripts/MyScripts").Include( "~/Scripts/*.js"));

Below is how your BundleConfig.cs file will look like:

public class BundleConfig { public static void RegisterBundles(BundleCollection bundles) { bundles.Add(new ScriptBundle("~/Scripts/MyScripts").Include(

"~/Scripts/*.js")); BundleTable.EnableOptimizations = true; } }

Once you have combined your scripts into one single unit we then to include all the JS files into the view using the below code. The below code needs to be put in the ASPX or Razor view.

<%= Scripts.Render("~/Scripts/MyScripts") %>

If you now see your page requests you would see that script request is combined into one request.

42) How can you test bundling in debug mode?

If you are in a debug mode you need to set EnableOptimizations to true in the bundleconfig.cs file or else you will not see the bundling effect in the page requests.

BundleTable.EnableOptimizations = true;

43) Explain minification and how to implement it?

Minification reduces the size of script and CSS files by removing blank spaces , comments etc. For example below is a simple javascript code with comments.

// This is test var x = 0; x = x + 1; x = x * 2;

After implementing minification the JavaScript code looks like below. You can see how whitespaces and comments are removed to minimize file size, thus increasing performance.

var x=0;x=x+1;x=x*2;

44) How do we implement minification?

When you implement bundling, minification is implemented by itself. In other words the steps to implement bundling and minification are the same.

45) Explain Areas in MVC?

Areas help you to group functionalities in to independent modules thus making your project more organized. For example in the below MVC project we have four controller classes and as time passes by if more controller classes are added it will be difficult to manage. In bigger

projects you will end up with 100’s of controller classes making life hell for maintenance.

If we can group controller classes in to logical section like “Invoicing” and “Accounting” that would make life easier and that’s what “Area” are meant to.

You can add an area by right clicking on the MVC solution and clicking on “Area” menu as shown in the below figure.

In the below image we have two “Areas” created “Account” and “Invoicing” and in that I have put the respective controllers. You can see how the project is looking more organized as compared to the previous state.

46) Explain the concept of View Model in MVC?

A view model is a simple class which represents data to be displayed on the view.

For example below is a simple customermodel object with “CustomerName” and “Amount” property.

CustomerViewModel obj = new CustomerViewModel(); obj.Customer.CustomerName = "Shiv";

obj.Customer.Amount = 1000;

But when this “Customer” model object is displayed on the MVC view it looks something as shown in the below figure. It has “CustomerName” , “Amount” plus “Customer Buying Level” fields on the view / screen. “Customer buying Level” is a color indicationwhich indicates how aggressive the customer is buying.

“Customer buying level” color depends on the value of the “Amount property. If the amount is greater than 2000 then color is red , if amount is greater than 1500 then color is orange or else the color is yellow.

In other words “Customer buying level” is an extra property which is calculated on the basis of amount.

So the Customer viewmodel class has three properties

“TxtCustomerName” textbox takes data from “CustomerName” property as it is.

“TxtAmount” textbox takes data from “Amount” property of model as it is.

“CustomerBuyingLevelColor” displays color value depending on the “Amount “ value.

Customer Model

Customer ViewModel

CustomerName TxtCustomerName

Amount TxtAmount

CustomerBuyingLevelColor

47) What kind of logic view model class will have?

As the name says view model this class has the gel code or connection code which connects the view and the model.

So the view model class can have following kind of logics:-

Color transformation logic: - For example you have a “Grade” property in model and you would like your UI to display “red” color for high level grade, “yellow” color for low level grade and “green” color of ok grade.

Data format transformation logic :-Your model has a property “Status” with “Married” and “Unmarried” value. In the UI you would like to display it as a checkbox which is checked if “married” and unchecked if “unmarried”.

Aggregation logic: -You have two differentCustomer and Address model classes and you have view which displays both “Customer” and “Address” data on one go.

Structure downsizing: - You have “Customer” model with “customerCode” and “CustomerName” and you want to display just “CustomerName”. So you can create a wrapper around model and expose the necessary properties.

How can we use two ( multiple) models with a single view?

Let us first try to understand what the interviewer is asking. When we bind a model with a view we use the model dropdown as shown in the below figure. In the below figure we can only select one model.

But what if we want to bind “Customer” as well as “Order” class to the view.

For that we need to create a view model which aggregates both the classes as shown in the below code. And then bind that view model with the view.

public class CustOrderVM { public Customer cust = new Customer(); public Order Ord = new Order(); }

In the view we can refer both the model using the view model as shown in the below code.

<%= model.cust.Name %> <%= model.Ord.Number %>

Download an e-learning copy of MVC interview Q&A from the top of this article for your preparation.

40) What are the new features of MVC2?

ASP.NET MVC 2 was released in March 2010. Its main features are:

Introduction of UI helpers with automatic scaffolding with customizable templates

Attribute-based model validation on both client and server Strongly typed HTML helpers Improved Visual Studio tooling There were also lots of API enhancements and “pro” features,

based on feedback from developers building a variety of applications on ASP.NET MVC 1, such as:

o Support for partitioning large applications into areas o Asynchronous controllers support o Support for rendering subsections of a page/site using

Html.RenderAction o Lots of new helper functions, utilities, and API

enhancements.


ASP.NET MVC 3 shipped just 10 months after MVC 2 in Jan 2011. Some of the top features in MVC 3 included:

The Razor view engine

Support for .NET 4 Data Annotations Improved model validation Greater control and flexibility with support for dependency

resolution and global action filters Better JavaScript support with unobtrusive JavaScript, jQuery

Validation, and JSON binding Use of NuGet to deliver software and manage dependencies

throughout the platform


Following are the top features of MVC4:

ASP.NET Web API Enhancements to default project templates Mobile project template using jQuery Mobile Display Modes Task support for Asynchronous Controllers Bundling and Minification

43) Explain “Request lifecycle” of an ASP.NET MVC?

Following processes are performed by ASP.NET MVC request:

1. App initialization 2. Routing 3. Instantiate and execute controller 4. Locate and invoke controller action 5. Instantiate and render view

45) What do you mean by Separation of Concerns?

As per Wikipedia, 'the process of breaking a computer program into distinct features that overlap in functionality as little as possible'. MVC design pattern aims to separate content from presentation and data-processing from content.

46) Where do we see Separation of Concerns in MVC?

Between the data-processing (Model) and the rest of the application.

When we talk about Views and Controllers, their ownership itself explains separation. The views are just the presentation form of an application, it does not have to know specifically about the requests coming from controller. The Model is independent of View and Controllers, it only holds business entities that can be passed to any View by the controller as required for exposing them to the end user. The controller is independent of Views and Models, its sole purpose is to handle requests and pass it on as per the routes defined and as per the need of rendering views. Thus our business entities (model), business logic (controllers) and presentation logic (views) lie in logical/physical layers independent of each other.

48) What is Unobtrusive JavaScript?

Unobtrusive JavaScript is a general term that conveys a general philosophy, similar to the term REST (Representational State

Transfer). The high-level description is that unobtrusive JavaScript doesn’t intermix JavaScript code in your page markup. For example, rather than hooking in via event attributes like onclick and onsubmit, the unobtrusive JavaScript attaches to elements by their ID or class, often based on the presence of other attributes (such as HTML5 data- attributes).

It’s got semantic meaning, and all of it — the tag structure, element attributes, and so on — should have a precise meaning. Strewing JavaScript gunk across the page to facilitate interaction (I’m looking at you, __doPostBack!) harms the content of the document.

49) What is JSON Binding?

MVC 3 included JavaScript Object Notation (JSON) binding support via the new JsonValueProviderFactory, enabling the action methods to accept and model-bind data in JSON format. This is especially useful in advanced Ajax scenarios like client templates and data binding that need to post data back to the server.

50) What is Dependency Resolution?

MVC 3 introduced a new concept called a dependency resolver, which greatly simplified the use of dependency injection in your applications. This made it easier to decouple application components, making them more configurable and easier to test.

Support was added for the following scenarios:

Controllers (registering and injecting controller factories, injecting controllers)

Views (registering and injecting view engines, injecting dependencies into view pages)

Action filters (locating and injecting filters) Model binders (registering and injecting) Model validation providers (registering and injecting) Model metadata providers (registering and injecting) Value providers (registering and injecting)

51) What are Display Modes in MVC4?

Display modes use a convention-based approach to allow selecting different views based on the browser making the request. The default view engine first looks for views with names ending with .Mobile.cshtml when the browser’s user agent indicates a known mobile device. For example, if we have a generic view titled Index.cshtml and a mobile view titled Index.Mobile.cshtml, MVC 4 will automatically use the mobile view when viewed in a mobile browser.

Additionally, we can register your own custom device modes that will be based on your own custom criteria — all in just one code statement. For example, to register a WinPhone device mode that would serve views ending with .WinPhone.cshtml to Windows Phone devices, you’d use the following code in the Application_Start method of your Global.asax:

DisplayModeProvider.Instance.Modes.Insert(0, new DefaultDisplayMode("WinPhone") { ContextCondition = (context => context.GetOverriddenUserAgent().IndexOf

("Windows Phone OS", StringComparison.OrdinalIgnoreCase) >= 0) });

52) What is AuthConfig.cs in MVC4?

AuthConfig.cs is used to configure security settings, including sites for OAuth login.

53) What is BundleConfig.cs in MVC4?

BundleConfig.cs in MVC4 is used to register bundles used by the bundling and minification system. Several bundles are added by default, including jQuery, jQueryUI, jQuery validation, Modernizr, and default CSS references.

54) What is FilterConfig.cs in MVC4?

This is used to register global MVC filters. The only filter registered by default is the HandleErrorAttribute, but this is a great place to put other filter registrations.

55) What is RouteConfig.cs in MVC4?

RouteConfig.cs holds the granddaddy of the MVC config statements, Route configuration.

56) What is WebApiConfig.cs in MVC4?

Used to register Web API routes, as well as set any additional Web API configuration settings.

57) What’s new in adding controller in MVC4 application?

Previously (in MVC3 and MVC2), the Visual Studio Add Controller menu item only displayed when we right-clicked on the Controllers folder. However, the use of the Controllers folder was purely for organization. (MVC will recognize any class that implements the IController interface as a Controller, regardless of its location in your application.) The MVC 4 Visual Studio tooling has been modified to display the Add Controller menu item for any folder in your MVC project. This allows us to organize your controllers however you would like, perhaps separating them into logical groups or separating MVC and Web API controllers.

58) What are the various types of Application Templates used to create an MVC application?

The various templates are as follows:

1. The Internet Application template: This contains the beginnings of an MVC web application — enough so that you can run the application immediately after creating it and see a few pages. This template also includes some basic account management functions which run against the ASP.NET Membership.

2. The Intranet Application template: The Intranet Application template was added as part of the ASP.NET MVC 3 Tools Update. It is similar to the Internet Application template, but the account

management functions run against Windows accounts rather than the ASP.NET Membership system.

3. The Basic template: This template is pretty minimal. It still has the basic folders, CSS, and MVC application infrastructure in place, but no more. Running an application created using the Empty template just gives you an error message.

Why use Basic template? The Basic template is intended for experienced MVC developers who want to set up and configure things exactly how they want them.

4. The Empty template: The Basic template used to be called the Empty template, but developers complained that it wasn’t quite empty enough. With MVC 4, the previous Empty template was renamed Basic, and the new Empty template is about as empty as we can get. It has the assemblies and basic folder structure in place, but that’s about it.

5. The Mobile Application template: The Mobile Application template is preconfigured with jQuery Mobile to jump-start creating a mobile only website. It includes mobile visual themes, a touch-optimized UI, and support for Ajax navigation.

6. The Web API template: ASP.NET Web API is a framework for creating HTTP services. The Web API template is similar to the Internet Application template but is streamlined for Web API development. For instance, there is no user account management functionality, as Web API account management is often significantly different from standard MVC account management. Web API functionality is also available in the other MVC project templates, and even in non-MVC project types.

59) What are the default Top level directories created when adding MVC4 application?

Default Top level Directories are:

DIRECTORY PURPOSE /Controllers To put Controller classes that handle URL requests /Models To put classes that represent and manipulate data and business objects /Views To put UI template files that are responsible for rendering output like HTML. /Scripts To put JavaScript library files and scripts (.js) /Images To put images used in your site /Content To put CSS and other site content, other than scripts and images /Filters To put filter code. /App_Data To store data files you want to read/write /App_Start To put configuration code for features like Routing, Bundling, Web API.

60) What is namespace of ASP.NET MVC?

ASP.NET MVC namespaces as well as classes are located in assembly System.Web.Mvc.

Note: Some of the content has been taken from various books/articles.

61) What is System.Web.Mvc namespace?

This namespace contains classes and interfaces that support the MVC pattern for ASP.NET Web applications. This namespace includes classes that represent controllers, controller factories, action results, views, partial views, and model binders.

62) What is System.Web.Mvc.Ajax namespace?

System.Web.Mvc.Ajax namespace contains classes that supports Ajax scripting in an ASP.NET MVC application. The namespace includes support for Ajax scripts and Ajax option settings as well.

63) What is System.Web.Mvc.Async namespace?

System.Web.Mvc.Async namespace contains classes and interfaces that support asynchronous actions in an ASP.NET MVC application.

64) What is System.Web.Mvc.Html namespace?

System.Web.Mvc.Html namespace contains classes that help render HTML controls in an MVC application. This namespace includes classes that support forms, input controls, links, partial views, and validation.

65) What is ViewData, ViewBag and TempData?

MVC provides us ViewData, ViewBag and TempData for passing data from controller, view and in next requests as well. ViewData and ViewBag are similar to some extent but TempData performs additional roles.

66) What are the roles and similarities between ViewData and ViewBag?

Maintains data when moving from controller to view

Passes data from controller to respective view Their value becomes null when any redirection occurs, because

their role is to provide a way to communicate between controllers and views. It’s a communication mechanism within the server call.

67) What are the differences between ViewData and ViewBag? (taken from a blog)

ViewData is a dictionary of objects that is derived from ViewDataDictionary class and accessible using strings as keys.

ViewBag is a dynamic property that takes advantage of the new dynamic features in C# 4.0.

ViewData requires typecasting for complex data type and checks for null values to avoid error.

ViewBag doesn’t require typecasting for complex data type.

NOTE: Although there might not be a technical advantage to choosing one format over the other, there are some critical differences to be aware of between the two syntaxes.

One obvious difference is that ViewBag works only when the key being accessed is a valid C# identifier. For example, if you place a value in ViewData["KeyWith Spaces"], you can’t access that value using ViewBag because the codewon’t compile.

Another key issue to be aware of is that dynamic values cannot be passed in as parameters to extension methods. The C# compiler must know the real type of every parameter at compile time in order for it to choose the correct extension method.

If any parameter is dynamic, compilation will fail. For example, this code will always fail: @Html.TextBox("name", ViewBag.Name). To work around this, either use ViewData["Name"] or cast the value to a specific type: (string) ViewBag.Name.

68) What is TempData?

TempData is a dictionary derived from the TempDataDictionary class and stored in short lives session. It is a string key and object value.

It keeps the information for the time of an HTTP Request. This means only from one page to another. It helps to maintain data when we move from one controller to another controller or from one action to other action. In other words, when we redirect Tempdata helps to maintain data between those redirects. It internally uses session variables. Temp data use during the current and subsequent request only means it is used when we are sure that the next request will be redirecting to next view. It requires typecasting for complex data type and checks for null values to avoid error. Generally it is used to store only one time messages like error messages, validation messages.

69) How can you define a dynamic property with the help of viewbag in ASP.NET MVC?

Assign a key name with syntax, ViewBag.[Key]=[ Value] and value using equal to operator.

For example, you need to assign list of students to the dynamic Students property of ViewBag.

List<string> students = new List<string>(); countries.Add("Akhil"); countries.Add("Ekta"); ViewBag.Students = students; //Students is a dynamic property associated with ViewBag.


70) What is ViewModel?

Accepted a view model represents data that you want to have displayed on your view/page.

Let's say that you have an Employee class that represents your employee domain model and it contains the following 4 properties:

public class Employee : IEntity { public int Id { get; set; } // Employee's unique identifier public string FirstName { get; set; } // Employee's first name public string LastName { get; set; } // Employee's last name public DateTime DateCreated { get; set; } // Date when employee was created }

View models differ from domain models in that view models only contain the data (represented by properties) that you want to use on your view. For example, let's say that you want to add a new employee record, your view model might look like this:

public class CreateEmployeeViewModel { public string FirstName { get; set; }

public string LastName { get; set; } }

As you can see, it only contains 2 of the properties of the employee domain model. Why is this you may ask? Id might not be set from the view, it might be auto generated by the Employee table. AndDateCreated might also be set in the stored procedure or in the service layer of your application. So Id and DateCreated is not needed in the view model.

When loading the view/page, the create action method in your employee controller will create an instance of this view model, populate any fields if required, and then pass this view model to the view:

public class EmployeeController : Controller { private readonly IEmployeeService employeeService; public EmployeeController(IEmployeeService employeeService) { this.employeeService = employeeService; } public ActionResult Create() { CreateEmployeeViewModel viewModel = new CreateEmployeeViewModel(); return View(viewModel); } public ActionResult Create(CreateEmployeeViewModel viewModel) {

// Do what ever needs to be done before adding the employee to the database } }

Your view might look like this (assuming you are using ASP.NET MVC3 and razor):

@model MyProject.Web.ViewModels.ProductCreateViewModel <table> <tr> <td><b>First Name:</b></td> <td>@Html.TextBoxFor(x => x.FirstName, new { maxlength = "50", size = "50" }) @Html.ValidationMessageFor(x => x.FirstName) </td> </tr> <tr> <td><b>Last Name:</b></td> <td>@Html.TextBoxFor(x => x.LastName, new { maxlength = "50", size = "50" }) @Html.ValidationMessageFor(x => x.LastName) </td> </tr> </table>

Validation would thus be done only on FirstName and LastName. Using Fluent Validation, you might have validation like this:

public class CreateEmployeeViewModelValidator : AbstractValidator<CreateEmployeeViewModel> { public CreateEmployeeViewModelValidator()

{ RuleFor(x => x.FirstName) .NotEmpty() .WithMessage("First name required") .Length(1, 50) .WithMessage("First name must not be greater than 50 characters"); RuleFor(x => x.LastName) .NotEmpty() .WithMessage("Last name required") .Length(1, 50) .WithMessage("Last name must not be greater than 50 characters"); } }

The key thing to remember is that the view model only represents the data that you want use. You can imagine all the unneccessary code and validation if you have a domain model with 30 properties and you only want to update a single value. Given this scenario, you would only have this one value/property in the view model and not the whole domain object.

71) How do you check for AJAX request with C# in MVC?

The solution is independent of MVC.NET framework and is global across server side technologies. Most modern AJAX applications utilize XmlHTTPRequest to send async request to the server. Such requests will have distinct request header:

X-Requested-With = XMLHTTPREQUEST

MVC.NET provides helper function to check for ajax requests which internally inspects X-Requested-With request header to set IsAjax flag.

72) What are Scaffold templates?

These templates use the Visual Studio T4 templating system to generate a view based on the model type selected. Scaffolding in ASP.NET MVC can generate the boilerplate code we need for create, read, update, and delete (CRUD) functionality in an application. The scaffolding templates can examine the type definition for, and then generate a controller and the controller’s associated views. The scaffolding knows how to name controllers, how to name views, what code needs to go in each component, and where to place all these pieces in the project for the application to work.

73) What are the types of Scaffolding Templates?

Various types are as follows:

SCAFFOLD DESCRIPTION Empty Creates empty view. Only the model type is specified using the model syntax. Create Creates a view with a form for creating new instances of the model.

Generates a label and input field for each property of the model type. Delete Creates a view with a form for deleting existing instances of the model. Displays a label and the current value for each property of the model. Details Creates a view that displays a label and the value for each property of the model type. Edit Creates a view with a form for editing existing instances of the model. Generates a label and input field for each property of the model type. List Creates a view with a table of model instances. Generates a column for each property of the model type. Make sure to pass an IEnumerable<YourModelType> to this view from your action method. The view also contains links to actions for performing the create/edit/delete operation.

75) What are Code Blocks in Views?

Unlike code expressions, which are evaluated and outputted to the response, blocks of code are simply sections of code that are executed. They are useful for declaring variables that we may need to use later.

Razor

@{ int x = 123;

string y = ?because.?; }

Aspx

<% int x = 123; string y = "because."; %>

76) What is HelperPage.IsAjax Property?

HelperPage.IsAjax gets a value that indicates whether Ajax is being used during the request of the Web page.

Namespace: System.Web.WebPages Assembly: System.Web.WebPages.dll

However, the same can be achieved by checking requests header directly:

Request["X-Requested-With"] == “XmlHttpRequest”.

77) Explain combining text and markup in Views with the help of an example?

This example shows what intermixing text and markup looks like using Razor as compared to Web Forms:

Razor

@foreach (var item in items) { <span>Item @item.Name.</span>

}

Aspx

<% foreach (var item in items) { %> <span>Item <%: item.Name %>.</span> <% } %>

78) Explain Repository Pattern in ASP.NET MVC?

In simple terms, a repository basically works as a mediator between our business logic layer and our data access layer of the application. Sometimes, it would be troublesome to expose the data access mechanism directly to business logic layer, it may result in redundant code for accessing data for similar entities or it may result in a code that is hard to test or understand. To overcome these kinds of issues, and to write an Interface driven and test driven code to access data, we use Repository Pattern. The repository makes queries to the data source for the data, thereafter maps the data from the data source to a business entity/domain object, finally and persists the changes in the business entity to the data source. According to MSDN, a repository separates the business logic from the interactions with the underlying data source or Web service. The separation between the data and business tiers has three benefits:

It centralizes the data logic or Web service access logic. It provides a substitution point for the unit tests. It provides a flexible architecture that can be adapted as the

overall design of the application evolves.

In Repository, we write our whole business logic of CRUD operations with the help of Entity Framework classes, that will not only result in

meaningful test driven code but will also reduce our controller code of accessing data.

79) How can you call a JavaScript function/method on the change of Dropdown List in MVC?

Create a JavaScript method:

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

80) Explain Routing in MVC?

A route is a URL pattern that is mapped to a handler. The handler can be a physical file, such as an .aspx file in a Web Forms application. Routing module is responsible for mapping incoming browser requests to particular MVC controller actions.

Routing within the ASP.NET MVC framework serves two main purposes:

It matches incoming requests that would not otherwise match a file on the file system and maps the requests to a controller action.

It constructs outgoing URLs that correspond to controller actions.

81) How route table is created in ASP.NET MVC?

When an MVC application first starts, the Application_Start() method in global.asax is called. This method calls the RegisterRoutes() method. The RegisterRoutes() method creates the route table for MVC application.

82) What are Layouts in ASP.NET MVC Razor?

Layouts in Razor help maintain a consistent look and feel across multiple views within our application. As compared to Web Forms, layouts serve the same purpose as master pages, but offer both a simpler syntax and greater flexibility.

We can use a layout to define a common template for your site (or just part of it). This template contains one or more placeholders that the other views in your application provide content for. In some ways, it’s like an abstract base class for your views.

E.g. declared at the top of view as:

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

83) What is ViewStart?

For group of views that all use the same layout, this can get a bit redundant and harder to maintain.

The _ViewStart.cshtml page can be used to remove this redundancy. The code within this file is executed before the code in any view placed in the same directory. This file is also recursively applied to any view within a subdirectory.

When we create a default ASP.NET MVC project, we find there is already a _ViewStart .cshtml file in the Views directory. It specifies a default layout:

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

Because this code runs before any view, a view can override the Layout property and choose a different one. If a set of views shares common settings, the _ViewStart.cshtml file is a useful place to consolidate these common view settings. If any view needs to override any of the common settings, the view can set those values to another value.


84) What are HTML Helpers?

HTML helpers are methods we can invoke on the HTML property of a view. We also have access to URL helpers (via the Url property), and AJAX helpers (via the Ajax property). All these helpers have the same goal: to make views easy to author. The URL helper is also available from within the controller. Most of the helpers, particularly the HTML helpers, output HTML markup. For example, the BeginForm helper is a

helper we can use to build a robust form tag for our search form, but without using lines and lines of code:

@using (Html.BeginForm("Search", "Home", FormMethod.Get)) { <input type="text" name="q" /> <input type="submit" value="Search" /> }

85) What is Html.ValidationSummary?

The ValidationSummary helper displays an unordered list of all validation errors in the ModelState dictionary. The Boolean parameter you are using (with a value of true) is telling the helper to exclude property-level errors. In other words, you are telling the summary to display only the errors in ModelState associated with the model itself, and exclude any errors associated with a specific model property. We will be displaying property-level errors separately. Assume you have the following code somewhere in the controller action rendering the edit view:

ModelState.AddModelError("", "This is all wrong!"); ModelState.AddModelError("Title", "What a terrible name!");

The first error is a model-level error, because you didn’t provide a key (or provided an empty key) to associate the error with a specific property. The second error you associated with the Title property, so in your view it will not display in the validation summary area (unless you remove the parameter to the helper method, or change the value to false). In this scenario, the helper renders the following HTML:

<div class="validation-summary-errors"> <ul> <li>This is all wrong!</li>

</ul> </div>

Other overloads of the ValidationSummary helper enable you to provide header text and set specific HTML attributes.

NOTE: By convention, the ValidationSummary helper renders the CSS class validation-summary-errors along with any specific CSS classes you provide. The default MVC project template includes some styling to display these items in red, which you can change in styles.css.

86) What are Validation Annotations?

Data annotations are attributes you can find in System.ComponentModel.DataAnnotations namespace. These attributes provide server-side validation, and the framework also supports client-side validation when you use one of the attributes on a model property. You can use four attributes in the DataAnnotations namespace to cover common validation scenarios,

Required, String Length, Regular Expression, Range.

87) What is Html.Partial?

The Partial helper renders a partial view into a string. Typically, a partial view contains reusable markup you want to render from inside multiple different views. Partial has four overloads:

public void Partial(string partialViewName); public void Partial(string partialViewName, object model);

public void Partial(string partialViewName, ViewDataDictionary viewData); public void Partial(string partialViewName, object model, ViewDataDictionary viewData);

88) What is Html.RenderPartial?

The RenderPartial helper is similar to Partial, but RenderPartial writes directly to the response output stream instead of returning a string. For this reason, you must place RenderPartial inside a code block instead of a code expression. To illustrate, the following two lines of code render the same output to the output stream:

@{Html.RenderPartial("AlbumDisplay"); } @Html.Partial("AlbumDisplay ")

If they are the same, then which one to use?

In general, you should prefer Partial to RenderPartial because Partial is more convenient (you don’t have to wrap the call in a code block with curly braces). However, RenderPartial may result in better performance because it writes directly to the response stream, although it would require a lot of use (either high site traffic or repeated calls in a loop) before the difference would be noticeable.

89) How do you return a partial view from controller?

return PartialView(options); //options could be Model or View name

90) What are different ways of returning a View?

There are different ways for returning/rendering a view in MVC Razor. E.g. return View(), return RedirectToAction(), return Redirect() and return RedirectToRoute().

92) What is ASP.NET MVC?

ASP.NET MVC is a web development framework from Microsoft that is based on MVC (Model-View-Controller) architectural design pattern. Microsoft has streamlined the development of MVC based applications using ASP.NET MVC framework.

100) 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.

101) What is namespace of ASP.NET MVC?

ASP.NET MVC namespaces and classes are located in the System.Web.Mvc assembly. System.Web.Mvc namespace

Contains classes and interfaces that support the MVC pattern for ASP.NET Web applications. This namespace includes classes that represent controllers, controller factories, action results, views, partial views, and model binders. System.Web.Mvc.Ajax namespace Contains classes that support Ajax scripts in an ASP.NET MVC application. The namespace includes support for Ajax scripts and Ajax option settings. System.Web.Mvc.Async namespace Contains classes and interfaces that support asynchronous actions in an ASP.NET MVC application. System.Web.Mvc.Html namespace Contains classes that help render HTML controls in an MVC application. The namespace includes classes that support forms, input controls, links, partial views, and validation.

102) 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.

103) 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 selecting the view to render.

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

In Application_Start event in Global.asax

107) 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.

108) 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.

109) What is the adavantage 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.

110) 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.

111) 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.

112) What is the use of the following statement? {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.

113) What is the difference between adding routes, to a webforms application and to an mvc application? To add routes to a webforms application, we use MapPageRoute() method of the RouteCollection class, where as to add routes to an MVC application we use MapRoute() method.

114) 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}/{*parametervalues}

115) What are the 2 ways of adding constraints to a route? 1. Use regular expressions 2. Use an object that implements IRouteConstraint interface

116) Give 2 examples for scenarios when routing is not applied? 1. A Physical File is Found that Matches the URL Pattern - This default behaviour can be overriden by setting the RouteExistingFiles property of the RouteCollection object to true. 2. Routing Is Explicitly Disabled for a URL Pattern - Use the RouteCollection.Ignore() method to prevent routing from handling certain requests.

117) What is the use of action filters in an MVC application? Action Filters allow us to add pre-action and post-action behavior to controller action methods.

118) If I have multiple filters implemented, what is the order in which these filters get executed? 1. Authorization filters 2. Action filters 3. Response filters 4. Exception filters

120) Give an example for Authorization filters in an asp.net mvc application? 1. RequireHttpsAttribute 2. AuthorizeAttribute

121) Which filter executes first in an asp.net mvc application? Authorization filter

122) What are the levels at which filters can be applied in an asp.net mvc application? 1. Action Method 2. Controller 3. Application

123) Is it possible to create a custom filter? Yes

124) What filters are executed in the end? Exception Filters

125) Is it possible to cancel filter execution? Yes

126) What type of filter does OutputCacheAttribute class represents? Result Filter

128) When using razor views, do you have to take any special steps to protect your asp.net mvc application from cross site scripting (XSS) attacks? No, by default content emitted using a @ block is automatically HTML encoded to protect from cross site scripting (XSS) attacks.

129) When using aspx view engine, to have a consistent look and feel, across all pages of the application, we can make use of asp.net master pages. What is asp.net master pages equivalent, when using razor views? To have a consistent look and feel when using razor views, we can make use of layout pages. Layout pages, reside in the shared folder, and are named as _Layout.cshtml

130) What are sections? Layout pages, can define sections, which can then be overriden by specific views making use of the layout. Defining and overriding sections is optional.

131) What are the file extensions for razor views? 1. .cshtml - If the programming lanugaue is C# 2. .vbhtml - If the programming lanugaue is VB

132) How do you specify comments using razor syntax? Razor syntax makes use of @* to indicate the beginning of a comment and *@ to indicate the end.

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

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

ASP.net MVC Interview Questions (1)

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