1. What is MVC?

Ans. MVC is a framework used to create web applications. The web application base builds on Model-View-Controller pattern which separates the application logic from UI, and the input and events from the user will be controlled by the Controller.

MVC stands for Model-View-Controller. It is a software design pattern which was introduced in 1970s. Also, MVC pattern forces a separation of concerns, it means domain model and controller logic are decoupled from user interface (view). As a result maintenance and testing of the application become simpler and easier.

2. Explain MVC design pattern?

Ans. MVC design pattern splits an application into three main aspects: Model, View and Controller

Model - The Model represents a set of classes that describe the business logic i.e. business model as well as data access operations i.e. data model. It also defines business rules for data means how the data can be changed and manipulated.

View - The View represents the UI components like CSS, jQuery, html etc. It is only responsible for displaying the data that is received from the controller as the result. This also transforms the model(s) into UI.

Controller - The Controller is responsible to process incoming requests. It receives input from users via the View, then process the user's data with the help of Model and passing the results back to the View. Typically, it acts as the coordinator between the View and the Model.

3. How MVC pattern works in ASP.NET MVC?

Ans. Working of MVC pattern in ASP.NET MVC is explained as below:

The Model in ASP.NET MVC

The Model in ASP.NET MVC can be broken down into several different layers as given below:

1. Objects or ViewModel or Presentation Layer - This layer contains simple objects or complex objects which are used to specify strongly-typed view. These objects are used to pass data from controller to strongly-typed view and vice versa. The classes for these objects can have specific validation rules which are defined by using data annotations. Typically, these classes have those properties which you want to display on corresponding view/page.

2. Business Layer - This layer helps you to implement your business logic and validations for your application. This layer make use of Data Access Layer for persisting data into database. Also, this layer is directly invoked by the Controller to do processing on input data and sent back to view.

3. Data Access Layer - This layer provides objects to access and manipulate the database of your application. Typically, this layer is made by using ORM tools like Entity Framework or NHibernate etc.

By default, models are stored in the Models folder of an ASP.NET MVC application.

The View in ASP.NET MVC

The view is only responsible for displaying the data that is received from the controller as a result. It also responsible for transforming a model or models into UI which provide all the required business logic and validation to the view.

By default, views are stored in the Views folder of an ASP.NET MVC application.

The Controller in ASP.NET MVC

The Controller in ASP.NET MVC, respond to HTTP requests and determine the action to take based upon the content of the incoming request. It receives input from users via the View, then process the user's data with the help of Model and passing the results back to the View.

By default, controllers are stored in the Controllers folder an ASP.NET MVC application.

4. How Model, View and Controller communicate with each other in ASP.NET MVC?

Ans. There are following rules for communication among Model, View and Controller:

1. User interacts with the Controller.

2. There is one-to-many relationship between Controller and View means one controller can mapped to multiple views.

3. Controller and View can have a reference to model.

4. Controller and View can talk to each other.

5. Model and View cannot talk to each other directly. They communicate to each other with the help of controller.

5. What are advantages of ASP.NET MVC?

Ans. There are following advantages of ASP.NET MVC over Web Forms (ASP.NET):

• Separation of concern - MVC design pattern divides the ASP.NET MVC application into three main aspects Model, View and Controller which make it easier to manage the application complexity.

• TDD - The MVC framework brings better support to test-driven development.

• Extensible and pluggable - MVC framework components were designed to be pluggable and extensible and therefore can be replaced or customized easier then Web Forms.

• Full control over application behavior - MVC framework doesn’t use View State or server based forms like Web Forms. This gives the application developer more control over the behaviors of the application and also reduces the bandwidth of requests to the server.

• ASP.NET features are supported - MVC framework is built on top of ASP.NET and therefore can use most of the features that ASP.NET include such as the providers architecture, authentication and authorization scenarios, membership and roles, caching, session and more.

• URL routing mechanism - MVC framework supports a powerful URL routing mechanism that helps to build a more comprehensible and searchable URLs in your application. This mechanism helps to the application to be more addressable from the eyes of search engines and clients and can help in search engine optimization.

6. What is difference between 3-layer architecture and MVC architecture?

Ans. 3-layer architecture separates the application into 3 components which consists of Presentation Layer Business Layer and Data Access Layer. In 3-layer architecture, user interacts with the Presentation layer. 3-layer is a linear architecture.

MVC architecture separates the application into three components which consists of Model, View and Controller. In MVC architecture, user interacts with the controller with the help of view. MVC is a triangle architecture.

MVC does not replace 3-layer architecture. Typically 3-layer and MVC are used together and MVC acts as the Presentation layer.

7. Explain ASP.NET MVC Pipeline/Page Life Cycle?

Ans. The detail ASP.NET MVC pipeline is given below:

1. Routing - Routing is the first step in ASP.NET MVC pipeline. Typically, it is a pattern matching system that matches the incoming request to the registered URL patterns in the Route Table.

The UrlRoutingModule(System.Web.Routing.UrlRoutingModule) is a class which matches an incoming HTTP request to a registered route pattern in the RouteTable(System.Web.Routing.RouteTable).

2. Controller Initialization - The MvcHandler initiates the real processing inside ASP.NET MVC pipeline by using ProcessRequest method. This method uses the IControllerFactory instance (default is System.Web.Mvc.DefaultControllerFactory) to create corresponding controller.

3. Action Execution – Action execution occurs in the following steps:

• When the controller is initialized, the controller calls its own InvokeAction() method by passing the details of the chosen action method. This is handled by the IActionInvoker.

• After chosen of appropriate action method, model binders(default is System.Web.Mvc.DefaultModelBinder) retrieves the data from incoming HTTP request and do the data type conversion, data validation such as required or date format etc. and also take care of input values mapping to that action method parameters.

• Authentication Filter was introduced with ASP.NET MVC5 that run prior to authorization filter. It is used to authenticate a user. Authentication filter process user credentials in the request and provide a corresponding principal. Prior to ASP.NET MVC5, you use authorization filter for authentication and authorization to a user.

• By default, Authenticate attribute is used to perform Authentication. You can easily create your own custom authentication filter by implementing IAuthenticationFilter.

• Authorization filter allow you to perform authorization process for an authenticated user. For example, Role based authorization for users to access resources.

• By default, Authorize attribute is used to perform authorization. You can also make your own custom authorization filter by implementing IAuthorizationFilter.

• Action filters are executed before (OnActionExecuting) and after (OnActionExecuted) an action is executed. IActionFilter interface provides you two methods OnActionExecuting and OnActionExecuted methods which will be executed before and after an action gets executed respectively. You can also make your own custom ActionFilters filter by implementing IActionFilter. For more about filters refer this article Understanding ASP.NET MVC Filters and Attributes

• When action is executed, it process the user inputs with the help of model (Business Model or Data Model) and prepare Action Result.

4. Result Execution - Result execution occurs in the following steps:

• Result filters are executed before (OnResultExecuting) and after (OnResultExecuted) the ActionResult is executed. IResultFilter interface provides you two methods OnResultExecuting and OnResultExecuted methods which will be executed before and after an ActionResult gets executed respectively. You can also make your own custom ResultFilters filter by implementing IResultFilter.

• Action Result is prepared by performing operations on user inputs with the help of BAL or DAL. The Action Result type can be ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult.

• Various Result type provided by the ASP.NET MVC can be categorized into two category- ViewResult type and NonViewResult type. The Result type which renders and returns an HTML page to the browser, falls into ViewResult category and other result type which returns only data either in text format, binary format or a JSON format, falls into NonViewResult category.

4.1 View Initialization and Rendering - View Initialization and Rendering execution occurs in the following steps:

• ViewResult type i.e. view and partial view are represented by IView (System.Web.Mvc.IView) interface and rendered by the appropriate View Engine.

• This process is handled by IViewEngine (System.Web.Mvc.IViewEngine) interface of the view engine. By default ASP.NET MVC provides WebForm and Razor view engines. You can also create your custom engine by using IViewEngine interface and can registered your custom view engine in to your ASP.NET MVC application as shown below:

• Html Helpers are used to write input fields, create links based on the routes, AJAX-enabled forms, links and much more. Html Helpers are extension methods of the HtmlHelper class and can be further extended very easily. In more complex scenario, it might render a form with client side validation with the help of JavaScript or jQuery.

8. Difference between ViewData, ViewBag, TempData, Session. Session Management in MVC

Ans : ViewData

• ViewData is a dictionary object that is derived from ViewDataDictionary class.

• publicViewDataDictionaryViewData { get; set; }

• ViewData is a property of ControllerBase class.

• ViewData is used to pass data from controller to corresponding view.

• Its life lies only during the current request.

• If redirection occurs then its value becomes null.

• It’s required typecasting for getting data and check for null values to avoid error.

Syntex:

Controller Code to assign data to ViewData.

ViewData["_firstName"] = _model.NameFirst;

Access ViewData value on View.

@Html.TextBox("FirstName", ViewData["FirstName"]

ViewBag

•

ViewBag is a dynamic property that takes advantage of the new dynamic features in C# 4.0., Whereas ViewBag not present in MVC 1.0,2.0,3.0.

• Basically it is a wrapper around the ViewData and also used to pass data from controller to corresponding view.

• publicObjectViewBag { get; }

• ViewBag is a property of ControllerBase class.

• Its life also lies only during the current request.

• If redirection occurs then its value becomes null.

• It doesn’t required typecasting for getting data.

Syntex:

Controller Code to assign data to ViewBag.

ViewBag.Message = "My message";

Access ViewBag value on View.

@Html.TextBox("Message",ViewBag.Message)

TempData

• TempData is a dictionary object that is derived from TempDataDictionary class and stored in short lives session.
• publicTempDataDictionaryTempData { get; set; }
• TempData is a property of ControllerBase class.
• TempData is used to pass data from current request to subsequent request (means redirecting from one page to another).
• Its life is very short and lies only till the target view is fully loaded.
• It’s required typecasting for getting data and check for null values to avoid error.
• It is used to store only one time messages like error messages, validation messages. To persist data with TempData.

Session

• Session is an object that is derived from HttpSessionState class.
• publicHttpSessionStateSession { get; }
• Session is a property of HttpContext class.
• Session is also used to pass data within the ASP.NET MVC application and Unlike TempData, it never expires.
• Session is valid for all requests, not for a single redirect.
• It’s also required typecasting for getting data and check for null values to avoid error.

9. What is difference between ASP.NET WebForm and ASP.NET MVC?

Ans. The main differences between ASP.NET Web Form and ASP.NET MVC are given below:

ASP.NET Web Forms	ASP.NET MVC
1. ASP.NET Web Form follows a traditional event driven development model.	1. ASP.NET MVC is a lightweight and follow MVC (Model, View, and Controller) pattern based development model.
2. ASP.NET Web Form has server controls.	2. ASP.NET MVC has html helpers.
3. ASP.NET Web Form has state management (like as view state, session) techniques.	3. ASP.NET MVC has no automatic state management techniques.
4. ASP.NET Web Form has file-based URLs means file name exist in the URLs must have its physically existence.	4. ASP.NET MVC has route-based URLs means URLs are divided into controllers and actions and moreover it is based on controller not on physical file.
5. ASP.NET Web Form follows WebForm Syntax	5. ASP.NET MVC follow customizable syntax (Razor as default)
6. In ASP.NET Web Form, Web Forms (ASPX) i.e. views are tightly coupled to Code behind (ASPX.CS) i.e. logic.	6. In ASP.NET MVC, Views and logic are kept separately.
7. ASP.NET Web Form has Master Pages for consistent look and feels.	7. ASP.NET MVC has Layouts for consistent look and feels.
8. ASP.NET Web Form has User Controls for code re-usability.	8. ASP.NET MVC has Partial Views for code re-usability.
9. ASP.NET Web Form has built-in data controls and best for rapid development with powerful data access.	9. ASP.NET MVC is lightweight, provide full control over mark-up and support many features that allow fast & agile development. Hence it is best for developing interactive web application with latest web standards.
10. ASP.NET Web Form is not Open Source.	10. ASP.NET Web MVC is an Open Source.

10. What is ViewModel in ASP.NET MVC?

Ans. In ASP.NET MVC, ViewModel is a class that contains the fields which are represented in the strongly-typed view. It is used to pass data from controller to strongly-typed view.

Key Points about ViewModel

• ViewModel contain fields that are represented in the view (for LabelFor, EditorFor, DisplayFor helpers)

• ViewModel can have specific validation rules using data annotations.

• ViewModel can have multiple entities or objects from different data models or data source.

11. What is Routing in ASP.NET MVC?

Ans. Routing is a pattern matching system that monitor the incoming request and figure out what to do with that request. At runtime, Routing engine use the Route table for matching the incoming request's URL pattern against the URL patterns defined in the Route table. You can register one or more URL patterns to the Route table at Application_Start event.

12. How to define a route in ASP.NET MVC?

Ans. You can define a route in ASP.NET MVC as given below:

// default Route

routes.MapRoute(

name: "Default",

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

defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }

13. What is difference between Routing and URL Rewriting?

Ans. Many developers compare routing to URL rewriting since both look similar and can be used to make SEO friendly URLs. But both the approaches are very much different. The main difference between routing and url rewriting is given below:

• URL rewriting is focused on mapping one URL (new url) to another URL (old url) while routing is focused on mapping a URL to a resource.

• URL rewriting rewrites your old url to new one while routing never rewrite your old url to new one but it map to the original route.

14. What are important namespaces in ASP.NET MVC?

Ans. There are some important namespaces as given below:

• System.Web.Mvc - 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.

• System.Web.Mvc.Ajax - This 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.

• System.Web.Mvc.Html – This 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.

15. What are Layouts in ASP.NET MVC?

Ans. Layouts are used to maintain a consistent look and feel across multiple views within ASP.NET MVC application. As compared to Web Forms, layouts serve the same purpose as master pages, but offer a simple syntax and greater flexibility.

16. What are Sections in ASP.NET MVC?

Ans. A section allow you to specify a region of content within a layout. It expects one parameter which is the name of the section. If you don’t provide that, an exception will be thrown. A section in a layout page can be defined by using the following code.

@section Footer
{
<p>Section/Index page</p>
}

You can render above defined section header on the content page as given below:

@RenderSection("footer", required: false)

By default, sections are mandatory. To make sections optional, just provides the second parameter value as false, which is a Boolean value.

@RenderSection("footer", false)

Note: A view can define only those sections that are referred to in the layout page otherwise an exception will be thrown

17. What are RenderBody and RenderPage in ASP.NET MVC?

Ans. RenderBody method exists in the Layout page to render child page/view. It is just like the ContentPlaceHolder on master page. A layout page can have only one RenderBody method

<body>

@RenderBody()

@RenderPage("~/Views/Shared/_Header.cshtml")

@RenderPage("~/Views/Shared/_Footer.cshtml")

@RenderSection("scripts",false)

@section scripts{

}

</body>

RenderPage method also exists in the Layout page to render other page exists in your application. A layout page can have multiple RenderPage method.

@RenderPage("~/Views/Shared/_Header.cshtml")

18. What are different ways of returning/rendering a view in ASP.NET MVC?

Ans. There are four different ways for returning/rendering a view in ASP.NET MVC as given below:

1. Return View() - This tells MVC to generate HTML to be displayed for the specified view and sends it to the browser. This acts like as Server.Transfer() in ASP.NET WebForm.

2. Return RedirectToAction() - This tells MVC to redirect to specified action instead of rendering HTML. In this case, browser receives the redirect notification and make a new request for the specified action. This acts like as Response.Redirect() in ASP.NET WebForm.

Moreover, RedirectToAction construct a redirect url to a specific action/controller in your application and use the route table to generate the correct URL. RedirectToAction cause the browser to receive a 302 redirect within your application and gives you an easier way to work with your route table.

3. Return Redirect() - This tells MVC to redirect to specified URL instead of rendering HTML. In this case, browser receives the redirect notification and make a new request for the specified URL. This also acts like as Response.Redirect() in ASP.NET WebForm. In this case, you have to specify the full URL to redirect.

Moreover, Redirect also cause the browser to receive a 302 redirect within your application, but you have to construct the URLs yourself.

4. Return RedirectToRoute() - This tells MVC to look up the specifies route into the Route table that is defined in global.asax and then redirect to that controller/action defined in that route. This also make a new request like RedirectToAction().

19. What are Action methods in ASP.NET MVC?

Ans. Controller actions are methods defined in the controller class and responsible to perform required operations on the user's inputs like as form values, query strings values etc. with the help of Model and passing the results back to the View. Asp.net MVC has the following built-in ActionResults Type and Helper methods:

1. ViewResult - Returns a ViewResult which renders the specified or default view by using controller View() helper method.

2. PartialViewResult - Returns a PartialViewResult which renders the specified or default partial view (means a view without its layout) by using controller PartialView() helper method.

3. RedirectResult - Returns a RedirectResult which Issues an HTTP 301 or 302 redirection to a specific URL by using controller Redirect() helper method.

4. RedirectToRouteResult - Returns a RedirectToRouteResult which Issues an HTTP 301 or 302 redirection to an action method or specific route entry by using controller RedirectToAction(), RedirectToActionPermanent(), RedirectToRoute(), RedirectToRoutePermanent() helper methods.

5. ContentResult - Returns a ContentResult which renders raw text like as "Hello, DotNet Tricks!" by using controller Content() helper method.

6. JsonResult - Returns a JsonResult which serializes an object in JSON format ( like as "{ "Message": Hello, World! }") and renders it by using controller Json() helper method.

7. JavaScriptResult - Returns a JavaScriptResult which renders a snippet of JavaScript code like as "function hello() { alert(Hello, World!); }" by using controller JavaScript() helper method. This is used only in AJAX scenarios.

8. FileResult - Returns a FileResult which renders the contents of a file like as PDF, DOC, Excel etc. by using controller File() helper method.

9. EmptyResult - Returns no result returned by an action. This has no controller helper method.

10. HttpNotFoundResult - Returns an HttpNotFoundResult which renders a 404 HTTP Status Code response by using controller HttpNotFound() helper method.

11. HttpUnauthorizedResult - Returns an HttpUnauthorizedResult which renders a 401 HTTP Status Code (means "not authorized") response. This has no controller helper method. This is used for authentication (forms authentication or Windows authentication) to ask the user to log in.

12. HttpStatusCodeResult - Returns an HttpStatusCodeResult which renders a specified HTTP code response. This has no controller helper method.

20. What is Data Annotations in ASP.NET MVC?

Ans. Data validation is a key aspect for developing web application. In Asp.net MVC, we can easily apply validation to web application by using Data Annotation attribute classes to model class. Data Annotation attribute classes are present in System.ComponentModel.DataAnnotations namespace and are available to Asp.net projects like Asp.net web application & website, Asp.net MVC, Web forms and also to Entity framework ORM models.

Data Annotations help us to define the rules to the model classes or properties for data validation and displaying suitable messages to end users.

Data Annotation Validator Attributes

• DataType - Specify the datatype of a property

• DisplayName - specify the display name for a property.

• DisplayFormat - specify the display format for a property like different format for Date property.

• Required - Specify a property as required.

• ReqularExpression - validate the value of a property by specified regular expression pattern.

• Range - validate the value of a property within a specified range of values.

• StringLength - specify min and max length for a string property.

• MaxLength - specify max length for a string property.

• Bind - specify fields to include or exclude when adding parameter or form values to model properties.

• ScaffoldColumn - specify fields for hiding from editor forms.

21. How to apply Server side validation in ASP.NET MVC?

Ans. Server side validations are very important before playing with sensitive information of a user. Server-side validation must be done whether we validate the received data on the client side. User could disable script in his browser or do something else to bypass client-side validation. In this case server-side validation must require to protect our data from dirty input.

In ASP.NET MVC, there are two ways to validate a model on server side:

Explicit Model Validation – This is the traditional way to validate the model data by using IF..Else..IF statement. In this way, you need to check your model property values one by one for your desired result. If model property values are unexpected, inject error messages within ModelState.

if (ModelState.IsValid)
{
//Model is valid. Call Service layer for further processing of data
} else {
//Validation failed. Return the model to the user with the relevant error messages
}

Model Validation with Data Annotations - Data Annotations was introduced with .NET 3.5 SP1. It has a set of attributes and classes defined in the System.ComponentModel.DataAnnotations assembly. Data Annotations allow us to decorate model classes with metadata. This metadata describes a set of rules that are used to validate a property.

[Required]
[StringLength(60, MinimumLength = 4)]
[Display(Name = "First Name")]
public string FirstName
{
get;
set;
}

22. How to enable and disable client-side validation in ASP.NET MVC?

Ans. We can enable and disable the client-side validation by setting the values of ClientValidationEnabled & UnobtrusiveJavaScriptEnabled keys true or false. This setting will be applied to application level.

For client-side validation, the values of above both the keys must be true. When we create new project using Visual Studio in MVC3 or MVC4, by default the values of both the keys are set to true.

We can also enable the client-side validation programmatically. For this we need to do code with in the Application_Start() event of the Global.asax, as shown below. protected void Application_Start()

{

//Enable or Disable Client Side Validation at Application Level

HtmlHelper.ClientValidationEnabled = true;

HtmlHelper.UnobtrusiveJavaScriptEnabled = true;

}

We can also enable or disable client-side validation for a specific view. For this we required to enable or disable client side validation inside a Razor code block as shown below. This option will overrides the application level settings for that specific view.

@using MvcApp.Models

ViewBag.Title = "About";

HtmlHelper.ClientValidationEnabled = false;

}

23. What is Bundling and Minification in ASP.NET MVC?

Ans. ASP.NET MVC4 and .NET Framework 4.5 offer bundling and minification techniques that reduce the number of request to the server and size of requested CSS and JavaScript, which improve page loading time.

A bundle is a logical group of files that is loaded with a single HTTP request. You can create style and script bundle for CSS and Java Scripts respectively by calling BundleCollection class Add() method. All bundles are create with in BundleConfig.cs file. public class BundleConfig

{

public static void RegisterBundles(BundleCollection bundles)

{

bundles.Add(new StyleBundle("~/Content/css").Include("~/Content/site.min.css",

"~/Content/mystyle.min.css"));

bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include(

www.dotnet-tricks.com Handy Tricks For Beginners & Professionals 51

"~/Scripts/jquery-1.7.1.min.js",

"~/Scripts/jquery.validate.min.js",

"~/Scripts/jquery.validate.unobtrusive.min.js"));

}

Minification is technique for removing unnecessary characters (like white space, newline, tab) and comments from the JavaScript and CSS files to reduce the size which cause improved load times of a webpage. There are so many tools for minifying the js and css files. JSMin and YUI Compressor are two most popular tools for minifying js and css files.

CSS and JS files Without Bundling and Minification

Suppose you have below CSS and JS files on the layout page and run the application in chrome browser and test no of request and loading time using chrome developer tools as shown below.

24. What is Partial View in ASP.NET MVC?

Ans. A partial view is like as user control in ASP.NET Web forms that is used for code re-usability. Partial views helps us to reduce code duplication. Hence partial views are reusable views like as Header and Footer views.

We can use partial view to display blog comments, product category, social bookmarks buttons, a dynamic ticker, calendar etc.

It is best practice to create partial view in the shared folder and partial view name is preceded by "_", but it is not mandatory. The "_" before view name specify that it is a reusable component i.e. partial view.

25. How do you return a partial view from controller?

Ans. return PartialView(options);

Where options could be a Model or a View name

26. What are different ways of rendering a Partial View in ASP.NET MVC?

Ans. There are four methods for rendering a partial view in ASP.NET MVC These are RenderPartial, RenderAction, Partial and Action helper methods.

Html.RenderPartial

• This method result will be directly written to the HTTP response stream means it used the same TextWriter object as used in the current webpage/template.

• This method returns void.

• Simple to use and no need to create any action.

• RenderPartial method is useful used when the displaying data in the partial view is already in the corresponding view model. For example: In a blog to show comments of an article, we would like to use RenderPartial method since an article information with comments are already populated in the view model.

• @{Html.RenderPartial("_Comments");}

This method is faster than Partial method since its result is directly written to the response stream which makes it fast.

Html.RenderAction

• This method result will be directly written to the HTTP response stream means it used the same TextWriter object as used in the current webpage/template.

• For this method, we need to create a child action for the rendering the partial view.

• RenderAction method is useful when the displaying data in the partial view is independent from corresponding view model. For example: In a blog to show category list on each and every page, we would like to use RenderAction method since the list of category is populated by the different model.

@{Html.RenderAction("Category","Home");}

This method is the best choice when you want to cache a partial view.

· This method is faster than Action method since its result is directly written to the HTTP response stream which makes it fast.

Html.Partial

• Renders the partial view as an HTML-encoded string.

• This method result can be stored in a variable, since it returns string type value.

• Simple to use and no need to create any action.

Partial method is useful used when the displaying data in the partial view is already in the corresponding view model. For example: In a blog to show comments of an article, we would like to use RenderPartial method since an article information with comments are already populated in the view model.

@Html.Partial("_Comments")

Html.Action

• Renders the partial view as an HtmlString .

• For this method, we need to create a child action for the rendering the partial view.

• This method result can be stored in a variable, since it returns string type value.

• Action method is useful when the displaying data in the partial view is independent from corresponding view model. For example: In a blog to show category list on each and every page, we would like to use Action method since the list of category is populated by the different model.

@{Html.Action("Category","Home");}

27. What is caching and when to use it?

Ans. Caching is a most important aspect of high-performance web application. Caching provides a way of storing frequently accessed data and reusing that data. Practically, this is an effective way for improving web application’s performance.

When to use caching

• Use caching for contents that are accessed frequently.

• Avoid caching for contents that are unique per user.

• Avoid caching for contents that are accessed infrequently/rarely.

• Use the VaryByCustom function to cache multiple versions of a page based on customization aspects of the request such as cookies, role, theme, browser, and so on.

• For efficient caching use 64-bit version of Windows Server and SQL Server.

• For database caching make sure your database server has sufficient RAM otherwise, it may degrade the performance.

• For caching of dynamic contents that change frequently, define a short cache–expiration time rather than disabling caching.

28. What are advantages of caching?

Ans. There are following advantages of caching:

• Reduce hosting server round-trips

• When content is cached at the client or in proxies, it cause minimum request to server.

• Reduce database server round-trips

• When content is cached at the web server, it can eliminate the database request.

• Reduce network traffic

• When content is cached at the client side, it also reduce the network traffic.

• Avoid time-consumption for regenerating reusable content

• When reusable content is cached, it avoid the time consumption for regenerating reusable content.

• Improve performance

• Since cached content reduce round-trips, network traffic and

29. What are the different Session state management options available in ASP.NET?

Ans : 1. In-Process

2. Out-of-Process.

In-Process stores the session in memory on the web server.

Out-of-Process Session state management stores data in an external server. The external server may be either a SQL Server or a State Server. All objects stored in session are required to be serializable for Out-of-Process state management.

30. What is boxing and unboxing?

Ans. Boxing is assigning a value type to reference type variable.

Unboxing is reverse of boxing i.e. Assigning reference type variable to value type variable.

31. Strongly typed view?

Ans: The view which bind with any model is called as strongly typed view. You can bind any class as model to view. You can access model properties on that view. You can use data associated with model to render controls.
You can bind custom types as well as primitive types like string, array, list etc. to view. e.g.

public class UserModel {}
Controller -
public ActionResult View1()
{
UserModel obj = new UserModel();
return view(obj)
}
View -
@model MyProject.UserModel

OR

Controller -
public ActionResult View1()
{
string[] arrStr = new string[5];
return view(arrStr)
}
View -
@model string[]

Again Main advantage of using strongly typed view is - You can same object during posting view. So Whater values assigned to controls associated models property. You can access in post action-

[HTTPPOST]
public ActionResult View1(UserModel obj)
{
obj.save();
return view();
}

It will be very using to post model at server side. Suppose we using strongly typed to add something. We can model details in post action and we can perform save operation on that object.

33. Attribute Routing

Ans: Routing in MVC and Web API is a pattern matching system that matches incoming request and figure out what to do with that request. Inside application Routing engine uses defined Route table for matching URI to an action. We have opportunity to define one or more routes in the route table. We register this route table in Application_Start (Global.asax) using following code.

Routing is a pattern matching process that monitors the requests and determines what to do with each request. In other words we can say Routing is a mechanism for mapping requests within our MVC application.

When a MVC application starts the first time, the Application_Start () event of global.asax is called. This event registers all routes in the route table using the RouteCollection.MapRoute method.

publicclass HomeController : Controller

{

[Route("Users/about")]

public ActionResult About()

{

ViewBag.Message = "You successfully reached USERS/About route";

return View();

}

[RoutePrefix("Movie")]

publicclass HomeController : Controller

     //Route: Movie/Index

      public ActionResult Index()

           ViewBag.Message = "You are in Home Index";

            return View();

//Route: Movie/About

public ActionResult About()

           ViewBag.Message = "You successfully reached USERS/About route";

            return View();

34. Difference between MVC2 Vs MVC3 Vs MVC4 Vs MVC5 Vs MVC6

Ans:

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

35. What is Dependency Injection?

Ans: In software engineering, dependency injection is a software design pattern that implements inversion of control for resolving dependencies. Dependency injection means giving an object its instance variables. Really. That's it.

The advantages of using the Dependency Injection pattern and Inversion of Control are the following:

·         Reduces class coupling
·         Increases code reuse
·         Improves code maintainability
·         Improves application testing

36. Understanding MVC, MVP and MVVM Design Patterns?

Ans: There are three most popular MV-* design patterns: MVC, MVP and MVVM. These are widely used by the various technologies. In this article, I will provide my opinion on these three.

MVC Pattern

MVC stands for Model-View-Controller. It is a software design pattern which was introduced in 1970s. Also, MVC pattern forces a separation of concerns, it means domain model and controller logic are decoupled from user interface (view). As a result maintenance and testing of the application become simpler and easier.

MVC design pattern splits an application into three main aspects: Model, View and Controller

1. Model

The Model represents a set of classes that describe the business logic i.e. business model as well as data access operations i.e. data model. It also defines business rules for data means how the data can be changed and manipulated.

2. View

The View represents the UI components like CSS, jQuery, html etc. It is only responsible for displaying the data that is received from the controller as the result. This also transforms the model(s) into UI.

3. Controller

The Controller is responsible to process incoming requests. It receives input from users via the View, then process the user's data with the help of Model and passing the results back to the View. Typically, it acts as the coordinator between the View and the Model.

Today, this pattern is used by many popular framework like as Ruby on Rails, Spring Framework, Apple iOS Development and ASP.NET MVC.

MVP pattern

This pattern is similar to MVC pattern in which controller has been replaced by the presenter. This design pattern splits an application into three main aspects: Model, View and Presenter.

1. Model

The Model represents a set of classes that describes the business logic and data. It also defines business rules for data means how the data can be changed and manipulated.

2. View

The View represents the UI components like CSS, jQuery, html etc. It is only responsible for displaying the data that is received from the presenter as the result. This also transforms the model(s) into UI.

3. Presenter

The Presenter is responsible for handling all UI events on behalf of the view. This receive input from users via the View, then process the user's data with the help of Model and passing the results back to the View. Unlike view and controller, view and presenter are completely decoupled from each other’s and communicate to each other’s by an interface.

Also, presenter does not manage the incoming request traffic as controller.

This pattern is commonly used with ASP.NET Web Forms applications which require to create automated unit tests for their code-behind pages. This is also used with windows forms.

Key Points about MVP Pattern:

1. User interacts with the View.

2. There is one-to-one relationship between View and Presenter means one View is mapped to only one Presenter.

3. View has a reference to Presenter but View has not reference to Model.

4. Provides two way communication between View and Presenter.

MVVM pattern

MVVM stands for Model-View-View Model. This pattern supports two-way data binding between view and View model. This enables automatic propagation of changes, within the state of view model to the View. Typically, the view model uses the observer pattern to notify changes in the view model to model.

1. Model

The Model represents a set of classes that describes the business logic and data. It also defines business rules for data means how the data can be changed and manipulated.

2. View

3. View Model

The View Model is responsible for exposing methods, commands, and other properties that helps to maintain the state of the view, manipulate the model as the result of actions on the view, and trigger events in the view itself.

This pattern is commonly used by the WPF, Silverlight, Caliburn, nRoute etc.

Key Points about MVVM Pattern:

1. User interacts with the View.

2. There is many-to-one relationship between View and ViewModel means many View can be mapped to one ViewModel.

3. View has a reference to ViewModel but View Model has no information about the View.

4. Supports two-way data binding between View and ViewModel.

What do you think?

I hope you have understand the MVC, MVP and MVVM design patterns. I would like to have feedback from my blog readers. Your valuable feedback, question, or comments about this article are always welcome.

37. What is Area in MVC?

Ans : Areas are an ASP.NET MVC feature used to organize related functionality into a group as a separate namespace (for routing) and folder structure (for views). Using areas creates a hierarchy for the purpose of routing by adding another route parameter, area, to controller and action.

Areas provide a way to partition a large ASP.NET Core MVC Web app into smaller functional groupings. An area is effectively an MVC structure inside an application. In an MVC project, logical components like Model, Controller, and View are kept in different folders, and MVC uses naming conventions to create the relationship between these components. For a large app, it may be advantageous to partition the app into separate high level areas of functionality. For instance, an e-commerce app with multiple business units, such as checkout, billing, and search etc. Each of these units have their own logical component views, controllers, and models. In this scenario, you can use Areas to physically partition the business components in the same project.

An area can be defined as smaller functional units in an ASP.NET Core MVC project with its own set of controllers, views, and models.

38. Authentication Filters?

Ans: So what is the real reason behind Authentication filters?

Prior to authentication filters, developers used the Authorization filters to drive some of the authentication tasks for the current request. It was convenient because the Authorization filters were executed prior to any other action filters. For example, before the request routes to action execution, we would use an Authorization filter to redirect an unauthenticated user to a login page. Another example would be to use the Authorization filter to set a new authentication principal, which is different from the application’s original principal in context.

Authentication related tasks can now be separated out to a new custom authentication filter and authorization related tasks can be performed using authorization filters. So it is basically about separating of concerns, while giving developers more flexibility to drive authentication using ASP.NET MVC infrastructure.

39. How to access globally TempData value in MVC?

TempData value in MVC?

TempData keep() vs peek()

When an object in a TempDataDictionary is read, it will be marked for deletion at the end of that request.

That means if you put something on TempData like

TempData["value"] = "someValueForNextRequest";

And on another request you access it, the value will be there but as soon as you read it, the value will be marked for deletion:

//second request, read value and is marked for deletion

object value = TempData["value"];

//third request, value is not there as it was deleted at the end of the second request

TempData["value"] == null

The Peek and Keep methods allow you to read the value without marking it for deletion. Say we get back to the first request where the value was saved to TempData.

With Peek you get the value without marking it for deletion with a single call.

//second request, PEEK value so it is not deleted at the end of the request

object value = TempData.Peek("value");

//third request, read value and mark it for deletion

object value = TempData["value"];

With Keep you specify a key that was marked for deletion that you want to keep. Retrieving the object and later on saving it from deletion are 2 different calls.

//second request, get value marking it from deletion

object value = TempData["value"];

//later on decide to keep it

TempData.Keep("value");

//third request, read value and mark it for deletion

object value = TempData["value"];

You can use Peek when you always want to retain the value for another request.

Use Keep when retaining the value depends on additional logic.

TempData is also a dictionary object that stays for the time of an HTTP Request. So, TempData can be used to maintain data between one controller action to the other controller action.

TempData is used to check the null values each time. TempData contain two method keep() and peek() for maintain data state from one controller action to others.

When TempDataDictionary object is read, At the end of request marks as deletion to current read object.

The keep() and peek() method is used to read the data without deletion the current read object.

You can use Peek() when you always want to hold/prevent the value for another request. You can useKeep() when prevent/hold the value depends on additional logic.

Overloading in TempData.Peek() & TempData.Keep() as given below.

TempData.Keep() have 2 overloaded methods.

1. void keep() : That menace all the data not deleted on current request completion.

2. void keep(string key) : persist the specific item in TempData with help of name.

TempData.Peek() no overloaded methods.

1. object peek(string key) : return an object that contain items with specific key without making key for deletion.

40. Types of constructor in MVC?

Types of Constructors

Basically constructors are 5 types those are

1. Default Constructor

2. Parameterized Constructor

3. Copy Constructor

4. Static Constructor

5. Private Constructor

41. What is Scaffolding in ASP.NET MVC?

Ans: Scaffolding is a technique used by many MVC frameworks like ASP.NET MVC, Ruby on Rails, Cake PHP and Node.JS etc., to generate code for basic CRUD (create, read, update, and delete) operations against your database effectively. Further you can edit or customize this auto generated code according to your need.

Scaffolding consists of page templates, entity page templates, field page templates, and filter templates. These templates are called Scaffold templates and allow you to quickly build a functional data-driven Website.

How Scaffold templates works in ASP.NET MVC.

Scaffold templates are used to generate code for basic CRUD operations within your ASP.NET MVC applications against your database with the help Entity Framework. These templates use the Visual Studio T4 templating system to generate views for basic CRUD operations with the help of Entity Framework.

Run time vs Design time Scaffolding Entity Framework.

Scaffolding can occur at two different phases of the program lifecycle: design time and run time. Design time scaffolding produces files of code that can later be modified by the programmer to customize the way the application database is used. However, for large-scale applications this approach may be difficult to maintain due to the sheer number of files produced, and the fact that the design of the files was largely fixed when they were generated or copied from the original templates.

Alternatively, run time scaffolding produces code on the fly. It allows changes to the design of the templates to be immediately reflected throughout the application. But modifying the design of the templates may be more difficult or impractical in the case of run time scaffolding.

42. Types of filters in MVC?

ASP.NET MVC Filters are used to inject extra logic at the different levels of MVC Framework request processing. Filters provide a way for cross cutting concern (logging, authorization, and caching).

Filter Type	Interface	Description
Authentication	IAuthenticationFilter	These are Runs, before any other filters or the action method.
Authorization	IAuthorizationFilter	These Runs first, before any other filters or the action method.
Action	IActionFilter	These Runs before and after the action method.
Result	IResultFilter	Runs before and after the action result is executed.
Exception	IExceptionFilter	Runs only if another filter, the action method, or the action result throws an exception.

43. What is AllowAnonymous attribute in mvc [Resolved]

For ex:

I have three pages named LOGIN, HOME, DETAILS.

Suppose that, we can access home, Details pages if we are authorized only.

To provide authorization we are using a login page.

Now, I want to provide authorization using [Authorize] filter defined in Filter.config file.

Then Authorization is applied to all pages (login also). Hence we cannot access login page also.

To allow login page access initially, we have to provide [AllowAnonymous] to login page.

Now, login page will open initially, after authorization, we can access remaining two pages

[AllowAnonymous] - Anyone can access view related to the action in controller

[Authorize] - Only registered users or specific set of users can access view related to the action in controller

You can also specify list of users in the attribute to grant access to them

44. What is html helpers in MVC?

Ans: Use of HTML helpers in a view to render HTML content. An HTML helper, in most cases, is just a method that returns a string.

You can build an entire ASP.NET MVC application without using a single HTML helper. However, HTML helpers make your life as a developer easier. By taking advantage of helpers, you can build your views with far less work.

45. What is Ajax Helpers in Asp.Net MVC?

Ans: In today modern era people want rich web applications for developing this kind application we need to use AJAX in one or other way. By using ajax helpers in asp.net mvc we can send data to server in asynchronous way without post backs that will make our applications interactive, easy to use and will make end user happy.

By using AJAX we can update partial part of view without posting entire page to server. Here we are going to see how to use AJAX helper in asp.net mvc to submit forms and using AJAX action link to invoke action method asynchronously by using JavaScript. Before starting with demo on AJAX helper let's have look on various properties of Ajax Options.

Di 46. Difference between ApiController and Controller in ASP.NET MVC?

3. Ans: Note If you have worked with ASP.NET MVC, then you are already familiar with controllers. They work similarly in Web API, but controllers in Web API derive from the ApiController class instead of Controller class. The first major difference you will notice is that actions on Web API controllers do not return views, they return data.

4. Use Controller to render your normal views. ApiController action only return data that is serialized and sent to the client.

5. ApiControllers are specialized in returning data. For example, they take care of transparently serializing the data into the format requested by the client. Also, they follow a different routing scheme by default (as in: mapping URLs to actions), providing a REST-ful API by convention.

6. You could probably do anything using a Controller instead of an ApiController with the some (?) manual coding. In the end, both controllers build upon the ASP.NET foundation. But having a REST-full API is such a common requirement today that WebAPI was created to simplify the implementation of a such an API.

7. It's fairly simple to decide between the two: if you're writing an HTML based web/internet/intranet application - maybe with the occasional AJAX call returning json here and there - stick with MVC/Controller. If you want to provide a data driven/REST-ful interface to a system, go with WebAPI. You can combine both, of course, having an ApiController cater AJAX calls from an MVC page.

Dot Net Crossway

Monday, 7 September 2020

MVC Interview Questions and Answers

33. Attribute Routing

36. Understanding MVC, MVP and MVVM Design Patterns?

MVC Pattern

1. Model

2. View

3. Controller

MVP pattern

1. Model

2. View

3. Presenter

Key Points about MVP Pattern:

MVVM pattern

1. Model

2. View

3. View Model

Key Points about MVVM Pattern:

What do you think?

Ans: So what is the real reason behind Authentication filters?

TempData keep() vs peek()

45. What is Ajax Helpers in Asp.Net MVC?

Constructor

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