MVC

Q1. What is MVC?

Ans. 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.

Q2. 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.

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

Q3. What is Domain Driven Design and Development?

Ans. Domain-Driven Design (DDD) is a collection of principles and patterns that help developers to take design decisions to develop elegant systems for different domains. It is not a technology or methodology.

The main components of DDD are: Entity, Value Object, Aggregate, Service and Repository.

Entity- An object that has an identity- it is unique within the system, like Customer, Employee etc.

Value Object- An object that has no identity within the system like Rate, State etc.

Note: A value object can become an entity depending on the situation.

Aggregate: An aggregate root is a special kind of entity that consumers refer to directly. All consumers of the aggregate root are called as aggregate. The aggregate root guarantees the consistency of changes being made within the aggregate.

Service- A service is a way of dealing with actions, operations and activities within your application.

Repository- A repository is responsible to store and to retrieve your data. It is not a concern how and where data will be persist. So, it can be SQL server, oracle, xml, text file or anything else. Repository is not a Data Access Layer but it refers to a location for storage, often for safety or preservation.

Q4. What is MVP pattern?

Ans. 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.

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.

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.

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.

Q5. What is MVVM pattern?

Ans. 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.

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.

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.

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.

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.

Q6. What is ASP.NET MVC?

Ans. ASP.NET MVC is an open source framework built on the top of Microsoft .NET Framework to develop web application that enables a clean separation of code. ASP.NET MVC framework is the most customizable and extensible platform shipped by Microsoft.

Q7. 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.

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.

Q8. 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.

Q9. What are advantages of ASP.NET MVC?

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

1. 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.

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

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

4. Full control over application behaviour - 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.

5. 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.

6.  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.

Q15. 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. When the routing engine finds a match in the route table for the incoming request's URL, it forwards the request to the appropriate controller and action. If there is no match in the route table for the incoming request's URL, it returns a 404 HTTP status code.

Q21. 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:

1.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.

2.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.

Q24. What are important namespaces in ASP.NET MVC?

Ans. There are some important namespaces as given below:

1. 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.

2. 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.

3. 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