Learning MVC Part 4 : Creating MVC Application with EntityFramework Code First Approach


Introduction

In our first three articles, we learnt a lot about MVC, starting from definition to use, from creating an application to connecting the MVC application with database using different techniques.
In the very last part of the series, we learnt how to connect our MVC application with existing database using Entity Framework.
This article will focus on connecting our MVC application with database using CodeFirst approach, i.e., one of the features Microsoft’s Entity Framework provides.

Our Roadmap

Just to remind our full roadmap towards learning MVC:
 

Pre-requisites

There are few pre-requisites before we start with the article:
  1. We have the running sample application that we created in the third part of the article series.
  2. We have EntityFramework 4.1 package or DLL on our local file system.
  3. We understand how MVC application is created.

Code-First Approach

To achieve a domain driven design, Entity Framework introduced EF 4.1 Code First. In the Code First approach, we focus on the domain design or entities/POCO classes first and create classes as per our model requirement. We do not have the database of the application, rather we create database automatically from code after defining our domain. The database created perfectly matches with the domain we design, so we have to be very conscious and keen in designing our domain model. It feels exciting to see database created on the fly with the help of our entities and XML configuration, without even opening database server.
No matter, you are not an expert in database, if you are a C# developer, just focus on your model/class creation.EntityFramework will take headache of creating and managing database for you.

Procedure

Step 1: Open the MVC application that we created in Learning MVC-Part3 in your Visual Studio.
We can clearly see and remember what we used to connect our MVC application to database with the help of entity framework, yes it was edmx class and our Model.tt classes generated from edmx classes.
Step 2: We don’t need the existing data-base, so you can delete the already created database for our part 3 application (if created).
Step 3: We don’t need edmx files now, so let’s clean our application, wipe out all these classes. Just deleteEFDataModel.edmxModel1.Context.tt and Model1.tt files. Now please do not run the application. It will give compile time errors, since we were using those classes ;-), Our solution will look like:
Our old solution had UserList class in Models folder, I have only changed the name of the class for differentiating it with previous application, and readability as was in the first part.
Step 4: As simple as that, just add a class to your solution, and name it MVCDBContext.cs as shown in the following image:
Step 5: Just add System.Data.Entity DLL as a reference to the solution if not already added.
Step 6: Use the namespace System.Data.Entity in our DBContext class, and inherit the added class fromDBContext class,
DbContext class: According to MSDN, DbContext class is conceptually similar to ObjectContext. To define, theObjectContext class is the part of the core EF API in the Microsoft .NET Framework 4 and this is our hero class that allows us to perform queries, change tracking and update the database using the strongly typed classes that represent our model (entity class). The DbContext is a wrapper around ObjectContext that exposes the most commonly used features of ObjectContext as well as provides some simpler “shortcuts” to tasks that are frequently used but complicated to code directly with ObjectContext. Simplfied alternative to ObjectContext and is the primary object for interacting with a database using a specific model.
Step 7: Add a DBSet property to the DbContext class that we created:
public DbSet Users { get; set; }
User, defined in angular brackets, is the model that we created in Models folder, so our MVCDBContext class looks like:
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Web;
using LearningMVC.Models;

namespace LearningMVC
{
public class MVCDBContext : DbContext
{
public DbSet Users { get; set; }
}
}

That’s it, our 90% work is done?
DbSet property: It is a simplified alternative to ObjectSet and is used to perform CRUD operations against a specific type from the model.
By default, the name of the DbContext class will be the name our database that will automatically be created, so be wise to select the name of context class, else it could be handled in web.config as well.
The name of model will be the name of Table in database and properties of model will be the columns of the table.

Our Heroes

Both DbContext and DbSet are our super heroes, in creating and dealing with database operations, and make us far abstracted, providing ease of use to us.
When we are working with DbContext, we are in real working with entity sets. DbSet represents a typed entity set that is used to perform create, read, update, and delete operations. We are not creating DbSet objects and using them indepedently. DbSet can be only used with DbContext.
Step 8: Define a connection string in web.config file, you can remove previously defined connection string, the new connection string will somewhat look like:
The name of the connection string will be the name of the DbContect that we defined, i.e., MVCDbContext.
Step 9: Now, we just have to modify the access method in controllers, earlier, when we created application in third part, we were accessing the context class from the modelcontext class that was generated from edmx file. Edmx file was added having reference to already created database.
But now the case is different, we don’t have a database now, we’ll access the table and columns using ourMVCDBContext class in controllers, so just change the following line of code used in Actions of earlier application:
var dbContext = new MVCEntities() ;
to
var dbContext = new MVCDBContext();
Job done. 
Just Hit F5, and you’ll see:
How does the application run, where is the database??? Dude, go back to your database server, and check for database:
We see our database is created, with the name MVCDB, that’s the magic of EntityFramework. Now we can perform all the CRUD operations on this database, using our application. Just create a new user.
In database we see, user created.
By default, integer property with ID in its name of model will be the primary key in the database, in our caseUserId, or you can define the primary key in the model too.

Conclusion

Now we know how to play with EntityFramework to create database as per our domain model from our code, we have already moved ahead to advanced concepts of MVC and Entity Framework.
When we see the definition of DbContext, it uses the terms Repository Pattern and Unit of Work Pattern. We’ll discuss these more in detail in my next article.

Read more:

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My other series of articles:

For more informative articles visit my Blog.

For more technical articles you can reach out to CodeTeddy.

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Learning MVC-Part 3 : Creating MVC Application & Perform CRUD Operations Using EntityFramework


                                      In our first and second attempt to learn MVC, we learnt, what is MVC?, what is separation of concerns?, how to create a simple MVC application and perform CRUD operations on the application using LINQ to SQL.
My this article focuses on how to perform CRUD operations in MVC application by the use of an ORM(Entity Framework).
The article is an attempt to overcome the confusion related to how to use EntityFramework with MVC application in a very simple way.
Our Roadmap:

Our roadmap remains same,

Pre-requisites:

There are few pre-requisites before we start with the article,
  •        We have running sample application that we created in second part of the article series.
  •        We have EntityFramework 4.1 package or dll on our local file system.
  •        We understand how MVC application is created.

What is ORM and EntityFramework?
The topic isn’t that scary as it seems to be. ORM(Object Relational Mapping) is basically an approach for storing data from domain/entity objects to relational database in an automated way without writing much code. A true ORM is independent of what database server we refer to, the code underlying ORM’s is database independent and can run with any database server having similar database with a structure needed by the application.ORM  has 3 main parts: Entity class objects, Relational db objects and information on how domain objects maps to relational db objects i.e. tables, views & storedprocedures. ORM helps us to keep our database design separate from our domain class design. This makes our application maintainable and extendable. It also automates standard CRUD operation (Create, Read, Update & Delete) so developer doesn’t require to code them manually J.
Now let’s have a look on standard definition of Entity Framework given by Microsoft:

“The Microsoft ADO.NET Entity Framework is an Object/Relational Mapping (ORM) framework that enables developers to work with relational data as domain-specific objects, eliminating the need for most of the data access plumbing code that developers usually need to write. Using the Entity Framework, developers issue queries using LINQ, then retrieve and manipulate data as strongly typed objects. The Entity Framework’s ORM implementation provides services like change tracking, identity resolution, lazy loading, and query translation so that developers can focus on their application-specific business logic rather than the data access fundamentals.

In a simple language, Entity framework is an Object/Relational Mapping (ORM) framework. It is an enhancement to ADO.NET, an upper layer to ADO.Net that gives developers an automated mechanism for accessing & storing the data in the database.
Hope this gives a glimpse of an ORM and EntityFramework.
EntityFramework Architecture:
Let’s have a glance over the architecture of EntityFramework,
        

                                                               

Our Web Application interacts with Entity Data Model (Entity Framework), that acts as an interface between ADO.Net Provider and database, fetches/saves data in the same flow as described in the figure.
Perform CRUD operations using EntityFramework on MVC application:
Open the existing Learning MVC application that we created using LINQ to SQL,

I have made few changes in the existing application, just to make it easy to understand when we implement EntityFramework in it.
1.Changed the model class name from User to UserList,
 
3.        namespace LearningMVC.Models
4.        {
5.            #region User Model...
6.            /// 
7.            /// User Model Class, purposely used for populating views and carry data from database.
8.            /// 
9.            public class UserList
10.           {
11.               #region Automated Properties
12.               public int UserId { get; set; }
13.               public string FirstName { get; set; }
14.               public string LastName { get; set; }
15.               public string EMail { get; set; }
16.               public string Address { get; set; }
17.               public string PhoneNo { get; set; }
18.               public string Company { get; set; }
19.               public string Designation { get; set; } 
20.               #endregion
21.           } 
22.           #endregion
23.       }
.
     2. Changed the Solution name from LearningMVC to LearningMVCWithEF.
Steps to Follow:
1. Open the application, modify it by above given changes.
2. Delete the MyDBML.dbml class from the solution.
3. Do not build the solution now, it will result in an error, as we have removed the dbml file, so controller method accessing the dbml file will throw compile time errors.
4. Goto project right click and add new item, select Data in installed templates and add ADO.Nety EntityDataModel to the application,
Name it EFDataModel.edmx.
5.New window will be opened to choose model contents,
Since we are following Database First approach, select generate From Database.

6.Choose the connection and give the name to connection string as MVCEntities as shown in the figure, click next.

7.Provide connection details to the existing database, that we used for our existing application, database name was MVC.
If you don’t have existing one, create a new one with the attached db script files.
8. Choose data base objects, we have only one table , so choose that one as shown in figure,
Give model namespace as MVCModel.
9.We get in our solution one guest,Entity Data Model that we saw in Entity Framework Architecture above,

10. In web.config you can see a new connection string is added.Now you can comment/delete old connection string of LINQ to SQL,
11. Generating Strongly Typed Entity Model Classes:(taken from a blog)
We’ll be working with the strongly typed entity classes now. The Entity Data Model designer uses a code generator in Visual Studio called the Text Template Transformation Toolkit (T4). Entity Framework will automatically generate a User class. The code generator nowwill create a class based on our Entity Data Model.
By default, the designer uses a template that results in entity classes that inherit from Entity Framework’s EntityObject and a container class which inherits from EF’s ObjectContext.
These base classes can be cumbersome to work with for a number of reasons. While the ObjectContext is extremely useful when you need a lot of control over Entity Framework’s behavior, the lighter weight DbContext provides access to the most commonly needed tasks and simplifies your coding.
Microsoft provides a number of alternative T4 templates for generating classes from the EDM.  When you installed the EF 4.1, a template for creating simpler classes including the DbContext was added to Visual Studio. Let’s tell the designer to use this template instead of the default.
·      Right click on the model’s designer surface.
·      From the context menu, choose Add Code Generation Item.
·      In the Add New Item dialog that opens, select Code from the list of installed templates types on the left.

·      Choose the ADO.NET DbContext Generator then click the Add button.

Two new files will be listed in Solution Explorer, Model1.Context.tt and Model1.tt. These are template files. Expand the templates to see the generated classes as shown in following figure,
12. When we open these two new guests, we see the context class to access model and model class for our user entity is already created, with full code,

Have you noticed that we have’nt written a single line of code by our hand, this is the revolution that EntityFramework has come up with, Let’s give a round of applause to our smart work,






Time to write some code now:
Till now we have not written a single line of code, but to access th context class, we need to change the logic from accessing LINQ to SQL data context to EntityFramework data context in the controller we created earlier in second part of the tutorial.
Steps to follow:
Step1: Bind all our views with UserList class, later it was user class, but we changed that to UserList class (remember????)
Step2:Open the controllers, change the access mechanism of context class as shown below for e.g. Index Action,
Earlier
public ActionResult Index()
{
var dbContext = new MyDBDataContext();
var userList = from user in dbContext.Users select user;
var users = new List();
if (userList.Any())
{
foreach (var user in userList)
{
users.Add(new LearningMVC.Models.User()
{ UserId = user.UserId, Address = user.Address,
Company = user.Company, FirstName = user.FirstName,
LastName = user.LastName, Designation = user.Designation,
EMail = user.EMail, PhoneNo = user.PhoneNo });
}
}
ViewBag.FirstName = "My First Name";
ViewData["FirstName"] = "My First Name";
if(TempData.Any())
{
var tempData = TempData["TempData Name"];
}
return View(users);
}
Now
public ActionResult Index()
{
var dbContext = new MVCEntities() ;
var userList = from user in dbContext.Users select user;
var users = new List();
if (userList.Any())
{
foreach (var user in userList)
{
users.Add(new LearningMVC.Models.UserList()
{ UserId = user.UserId, Address = user.Address,
Company = user.Company, FirstName = user.FirstName,
LastName = user.LastName, Designation = user.Designation,
EMail = user.EMail, PhoneNo = user.PhoneNo });
}
}
ViewBag.FirstName = "My First Name";
ViewData["FirstName"] = "My First Name";
if(TempData.Any())
{
var tempData = TempData["TempData Name"];
}
return View(users);
}
You can see we just had to change access mechanism, mere change of 2-3 lines, and not anything in the logic of application.
Step3: Like wise do the same for all the Actions. I am not showing how to do here, but you can compare the source codes and now can do by yourself.
Step4: Note LINQ to SQL context class uses InsertOnSubmit()/DeleteOnSubmit() and SubmitChanges() method for Insert, update,Delete but EF context class uses .Add(), .SaveChanges().So do it skillfully when required.
Step5: All set now, rebuild your application, and you’ll not get a single error.Now ready to run.
Step6: When you run the application, it runs as was running previously and now you can perform CRUP operations as an end user to the application, and test the application .

Nothing more dude, we are done with Entity framework’s database first approach now.You can applause again, and take some rest.
 
Conclusion:
We have already moved to one step on advanced level of CRUD operations in MVC.There is more to learn in MVC and Entity Framework, that we’ll be covering in upcoming articles.In this article we mastered how to perform CRUD operations in MVC application using EntityFramework’s database first approach,next article will focus on my favourite CodeFirst approach J.
Happy Coding.

Learning MVC-Part 2 :Creating MVC Application & Perform CRUD operations using LINQ to SQL


Introduction:
                           In first part of the tutorial series we got a glimpse of MVC. In this part we’ll focus on practical implementation of MVC Pattern. I don’t need to  explain about theory of MVC as we have already covered this in previous part of the article.
 
Our Roadmap:
 
                      We stick our agenda as follows,
 
Topics to be covered:
1.     Creating MVC project from scratch.
2.     Adding Controllers, Views and Models.
3.     Creating sample database and use LINQ to SQL for communication.
4.     Perform CRUD operations in MVC application using LINQ to SQL.
5.     Understand ViewData, ViewBag and TempData.
6.     Model Validation by System.Component.DataAnnotation.
1.    Creating MVC project:
     Step1: Open Visual Studio 2010/2013,I am using 2010.Goto File=>New=>Project and select  ASP.Net MVC3 Web Application, as shown below,
 
 
Name the application as LearningMVC.
 
Step2: A project template selection window will be opened, select Empty in that.Select View Engine as Razor and press OK.
 
 
Step3: Now our solution is ready with an empty MVC application,
 
We can clearly see that the solution contains some extra folders in comparison to traditional Asp.Net web application.
We got Models, Views and Controllers folder and a Shared folder in Views folder. The folders as name denotes are used to hold the respective MVC players model-view-controllers, the shared folder in Views contains the _Layout.cshtml, that can be used as the master page for the views which we create.
We see the global.asax file that contains a default routing table, that defines the route to be followed when request comes, it says that when request comes to Home controller, the Index action of that Home Controller has to be called,
 
Actions are the methods defined in Controllers, that can be called defining a route, the Action methods can also contain parameters, in above mentioned figure, it says that Home controller has an Action Index which contains an optional parameter id.
When we run our application, we get something as shown below,
 
It says that the resource which we are looking for can not be found.The request by default follows the default route as mentioned in global.asax, i.e. go to controller Home and invoke method Index.Since we don’t have any of these yet, the browser shows this error.
Never mind, lets make the browser happy.
2.  Adding Controllers ,View and Models:
Step1: Create a My Controller by right clicking on Controllers folder and add a controller named My, add the controller with empty read/write actions, it will give us a class with few default generated actions.
 
Note that there are two Actions for every Action name, one is for Get i.e. when view loads for first time, and second one is for POST, when View is submitted with some data.
Change global.asax RegisterRoutes method as,
  public static void RegisterRoutes(RouteCollectionroutes)
        {
            routes.IgnoreRoute(“{resource}.axd/{*pathInfo}”);
            routes.MapRoute(
                “Default”, // Route name
                “{controller}/{action}/{id}”, // URL with parameters
                new { controller = “My”, action = “Index”, id = UrlParameter.Optional } // Parameter defaults
            );
        }
Note: we have changed the name of controller as per our added controller.
Step2: We can see that we have Actions but they return a View, so we need to create Views for them.But before this we’ll create a Model named User for our Views.Right click on Model folder add a class named User,
Add following properties to User class,
Now our model is created and we can create Views bound to this particular model.
 
Step3: Go to controller, right click on empty Actions of the controller and from the context menu select AddView on the top.By default the View name is same as of Actions name.
e.g. For Details,
 
 
Select Viewname as Details,Model class as User, and Scaffold Template as Details.This template specifies the role of the View, that this view will show the details of the User(entity).Click add.
Likewise perform this operation for all the Actions, and create Views.
Note that Views are automatically added, to Views folder under My folder(auto created as per Controller’s name).This is to maintain a particular structure for MVC, so that we don’t have to take overhead to maintain it.
 

 

 

 


   Now we have controller as well as Views, so if we run the application we get,

 
i.e. Index Action of our My controller is Fired that returned Index View. 
 
 
 
3. Creating sample database and use LINQ to SQL for communication.
                         
                        Our MVC application is ready but, rather than displaying dummy data, I would go for running the application talking to a data base so that we can cover wider aspect of the application.
 
Step1: Create a database, script is given in the attachment, just execute it over Sql Server 2005/2008.
 
Step2: Add new Item to the solution, and select LINQ to SQL class, call it MyDB.dbml
 
Our Solution looks like,
Step3:Open Server explorer of Visual Studio, Open a connection, by providing Server name and existing database name in Server Explorer Open Connection window,

 

Click OK.Our solution looks like,
Step4: Drag the User table to dbml designer window,we get the table in class diagram format in designer window,
 
When we open MyDB.designer.cs, we get MyDBDataContext class.This class holds databse User table information in the form of Class and Properties.For every column of the table, properties are created in the class, and we can use these properties to get/set values from/in database.
4. Perform CRUD operations in MVC application using LINQ to SQL.

We now have a database, a context class to talk to data base and a MVC application to perform CRUD operations in database using the context class.
Step1 Read :
 
i) Go to Index Action, make an instance of context class, We can get all the table and column names in that context’s instance.
ii) Make a query to display all the records on Index view.
iii) Populate the User Model that we created earlier, and pass it to the Index view(Index View will be of List type Item template)
When we run the application, we get empty list, i.e. we don’t have records in database,
 
Step2 Create:
i)First write code for creating a user, for the first time for Get Action of create, always an empty view will be returned.
 
ii)When we post some data on click of submit of Create, then we need to make a data entry in table for creating a new user.
iii)When form posted, it fires Post Action of Create with the already bound User model properties to view fields, we’ll retrieve these model properties and make an instance of context class populate context User and submit to data base.
 
 
 iv)Redirect action to Index, and now a record will be shown on the Index View.We successfully created a user J.
 

v) In database :

Step3 Update & Step4 Delete:
Now we are smart enough to perform update and delete by ourself, this I leave for reader’s understanding capabilities, below are the screens for Update and  Delete.
Edit Code:
 
Get:
Post:
Get Action View of Edit:
 
Edited few fields:
 
Update reflected in database:
 
Code to show details of a particular user :
 
Details Screen:
 
Note : Details Action do not have POST one, as nothing to post to controller.
Likewise for Delete:
 
Screen:
Back to List after Delete:
 
 
In database after delete:
 
Yes, all the CRUD operations done.Now we know MVC.
There are few basic scenarios that I want to discuss before finishing with the First Part, like passing data from Controller to Views, between Controllers etc and about Model validation.
5. Understand ViewData, ViewBag and TempData.
 
I wanted to take this topic as there is much confusion  regarding these three players.
MVC provides us ViewData, VieBag 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. Lets get key points on these three players:
ViewBag & ViewData :
I have written sample test code in the same application which we are following from the beginning,
         Populate ViewData and ViewBag on Index action of My Controller,
         Code in View to fetch ViewData/ViewBag,
 
         When run the application, we get on screen,
 
Following are roles and similarities between ViewData and ViewBag:
 
Ø  Maintains data when move from controller to view.
Ø  Passes data from controller to respective view.
Ø  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.
Differences between ViewData and ViewBag (taken from a blog):
 
Ø ViewData is a dictionary of objects that is derived from ViewDataDictionary class and accessible using strings as keys.
Ø ViewBag is a dynamic property that takes advantage of the new dynamic features in C# 4.0.
Ø ViewData requires typecasting for complex data type and check for null values to avoid error.
Ø ViewBag doesn’t require typecasting for complex data type.
TempData:
 
TempData is a dictionary derived from TempDataDictionary class and stored in short lives session.It is a string key and object value.
It keep the information for the time of an HTTP Request. This mean only from one page to another. Helps to maintain data when we move from one controller to other 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 use when we are sure that next request will be redirecting to next view. It requires typecasting for complex data type and check for null values to avoid error. Generally it is used to store only one time messages like error messages, validation messages.
I added a TempData in Edit Action as,
[HttpPost]
        public ActionResultEdit(int? id, UseruserDetails)
        {
            TempData[“TempData Name”] = “Akhil”;
                 …..
And when View redirected to Index Action,
i.e. I get the TempData value across Actions.
6.Model Validation:
 
 We can have many methods for implementing validation in our Web Application Client Side, Server Side etc…
 But MVC provides us a feature with which we can annotate our Model for validation by writing just one/two line of code.
 Go to the Model class User.cs, add [Required(ErrorMessage = “FirstName is required”)] on the top of FirstName property as,
public int UserId { get; set; }
        [Required(ErrorMessage = “FirstName is required”)]
        public stringFirstName { get; set; }
        public stringLastName { get; set; }
………..
 
Now when we run the application, and try to Edit/Create user without specifying FirstName, we get,
 
Surprised!, Yes model validates itself with these annotations, there are many more validators like required field one that I used.
Do not forget to include usingSystem.ComponentModel.DataAnnotations; Namespace, when using Model Validation.This is the namespace that holds classes used for validation.
Conclusion:
                 Now we know what MVC is ,how to Implement it,its advantages,CRUD operations in MVC.Upcoming parts of the tutorial will be focussing on more advanced topics like EntityFramework, Repository Pattern,Unit Of Work Pattern.Code First Approach.

 

Happy Coding J.

Read more:

Other Series

My other series of articles:

For more informative articles visit my Blog.

For more technical articles you can reach out to CodeTeddy.

Learning MVC-Part 1 : Introduction to MVC Architecture and Separation of Concerns


Introduction:
 
After having gone through numerous of blogs and articles, I came to a conclusion that very few of the genuine writers have explained the topic from basics to its details in a full-fledged way with a working application. My effort in this MVC articles series would be to cover almost all the aspects of MVC starting from creating simple app and connecting with the database with various Microsoft providers. We’ll be gradually moving forward part by part to understand and practically implement all the scenarios.
Road Map:
All set, now we can start our journey with Part1.
Part1: Introduction to MVC architecture and Separation of Concerns.
Topics to be covered:
  • 1.     What does MVC mean.
  • 2.     Understand MVC Architecture.
  • 3.     Separation of Concerns

 

Players:
Model: The business entity on which the overall application operates. Many applications use a persistent storage mechanism (such as a database) to store data. MVC does not specifically mention the data access layer because it is understood to be encapsulated by the Model.
View: The user interface that renders the model into a form of interaction.
Controller: Handles a request from a view and updates the model that results a change in Model’s state.
To implement MVC in .NET we need mainly three classes (View, Controller and the Model).
MVC Architecture:
           The choice of MVC comes when we go for a solution where separation of concerns, ease of maintainability and extensibility of an application matters a lot. As per the architecture given below, we can see the request-response flow of a MVC application.

The architecture is self explanatory in itself. Browser as usual sends a request to IIS,IIS searches for the route defined in MVC application and passes request to the controller as per route, the controller communicates with model and passes the populated model(entity) to View(front end), Views are populated with model properties, and are rendered on the browser, passing the response to browser through IIS via controllers which invoked the particular View.

Separation of Concern:
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. Theoretically well, but where do we see this in MVC? One is reasonably clear – 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 controller as per need of exposing them to end user.The controller in independent of Views and Models, its sole purpose is to handle requests and pass it on as per the routes defined and as per 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.
Conclusion:
Now we know why and where to use MVC, in another part of learning MVC we’ll be creating a MVC application from scratch, exploring the practical implementation of MVC.

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ASP.Net MVC Interview Questions and Answers


Introduction:
My this article on Interview Questions and Answers of MVC basically covers most of the MVC 2, MVC3 and MVC4 topics that are more likely to be asked in job interviews/tests/exams.
The sole purpose of this article is to sum up important questions and answers that can be used by developers to brush-up all about MVC before they take any interview of the same kind.
What is MVC?
MVC is a framework pattern that splits an application’s implementation logic into
three component roles: models, views, and controllers.
  • Model: The business entity on which the overall application operates. Many applications use a persistent storage mechanism (such as a database) to store data. MVC does not specifically mention the data access layer because it is understood to be encapsulated by the Model.
  • View: The user interface that renders the Model into a form of interaction.
  • Controller: Handles a request from a View and updates the Model that results in a change of the Model’s state.
To implement MVC in .NET we need mainly three classes (View, Controller and the Model).
Explain MVC Architecture?
 
The architecture is self explanatory. The browser (as usual) sends a request to IIS, IIS searches for the route defined in MVC application and passes the request to the controller as per route, the controller communicates with the model and passes the populated model (entity) to View (front end), Views are populated with model properties, and are rendered on the browser, passing the response to browser through IIS via controllers which invoked the particular View.

What are the new features of MVC2?
ASP.NET MVC 2 was released in March 2010. Its main features are:
  1.       Introduction of UI helpers with automatic scaffolding with customizable templates.
  2.       Attribute-based model validation on both client and server.
  3.        Strongly typed HTML helpers.
  4.        Improved Visual Studio tooling
  5.       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:

  •   Support for partitioning large applications into areas.
  •   Asynchronous controllers support.
  •   Support for rendering subsections of a page/site using Html.RenderAction.
  •   Lots of new helper functions, utilities, and API enhancements

What are the new features of MVC3?

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.

What are the new features of MVC4?
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.

Explain “page lifecycle” of an ASP.NET MVC?
Following process are performed by ASP.Net MVC page:
  1.  App initialization
  2.  Routing
  3.  Instantiate and execute controller
  4.  Locate and invoke controller action
  5.  Instantiate and render view
Advantages of MVC Framework?
  1.  Provides a clean separation of concerns between UI (Presentation layer), model (Transfer objects/Domain Objects/Entities) and Business Logic (Controller).
  2.  Easy to UNIT Test.
  3.  Improved reusability of views/model. One can have multiple views which can point tosame model and vice versa.
  4.  Improved structuring of the code.
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.
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.
What is Razor View Engine?
Razor is the first major update to render HTML in MVC3. Razor was designed specifically as a view engine syntax. It has one main focus: codefocused templating for HTML generation. Here’s how that same markup would be generated using Razor:
@model MvcMusicStore.Models.Genre
@{ViewBag.Title = “Browse Albums”;}
<div class=”genre”>
<h3><em>@Model.Name</em> Albums</h3>
<ul id=”album-list”>
@foreach (var album in Model.Albums)
{
<li>
<a href=”@Url.Action(“Details”, new { id = album.AlbumId })”>
<img alt=”@album.Title src=”@album.AlbumArtUrl />
<span>@album.Title</span>
</a>
</li>
}
</ul>
</div>
The Razor syntax is easier to type, and easier to read. Razor doesn’t have the XML-like heavy syntax.
of the Web Forms view engine.
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.
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.
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 fi lters (locating and injecting fi lters)
  •       Model binders (registering and injecting)
  •       Model validation providers (registering and injecting)
  •       Model metadata providers (registering and injecting)
  •       Value providers (registering and injecting)

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 fi rst 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)
});
What is AuthConfig.cs in MVC4?
AuthConfig.cs  is used to configure security settings, including sites for OAuth login.
 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.
 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.
 What is  RouteConfig.cs in MVC4?
 RouteConfig.cs holds the granddaddy of the MVC config statements, Route configuration.
 What is WebApiConfig.cs in MVC4?
 Used to register Web API routes, as well as set any additional Web API configuration settings.
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.
What are the software requirements of ASP.NET MVC4 application?
MVC 4 runs on the following Windows client operating systems:
  •     Windows XP
  •     Windows Vista
  •     Windows 7
  •     Windows 8

It runs on the following server operating systems:
  •     Windows Server 2003
  •     Windows Server 2008
  •     Windows Server 2008 R2

MVC 4 development tooling is included with Visual Studio 2012 and can be installed on Visual
Studio 2010 SP1/Visual Web Developer 2010 Express SP1.
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 signify-cantly 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.
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.
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.
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.
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.
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.
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.
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.
What are the roles and similarities between ViewData and ViewBag?
  • Maintains data when move 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.
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 check 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 specifi c type: (string) ViewBag.Name.
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 keep 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 use when we are sure that next request will be redirecting to next view. It requires typecasting for complex data type and check for null values to avoid error. Generally it is used to store only one time messages like error messages, validation messages.
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 students = new List();
countries.Add(“Akhil”);
countries.Add(“Ekta”);
ViewBag.Students = students;
//Students is a dynamic property associated with ViewBag.
Note: Some of the content has been taken from various books/articles.
What is ViewModel(taken from stackoverflow)?
First Name:</b></td>
         
.TextBoxFor(x => x.FirstName, new { maxlength = “50”, size = “50” })
              @Html.ValidationMessageFor(x => x.FirstName)
         
accepted
A view model represents data that you want to have displayed on your view/page.
Lets 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, lets 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 need 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
    
         
@Html
     

     
           Last Name:</b></td>
          @Html.TextBoxFor(x => x.LastName, new { maxlength = “50”, size = “50” })
              @Html.ValidationMessageFor(x => x.LastName)
          

     

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 uneccessary 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.
How do you check for AJAX request with C# in MVC.NET?
The solution is independed 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.
What are Scaffold template?
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.
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 fi eld 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 to this view from your action method.
                               The view also contains links to actions for performing the create/edit/delete                                                                                       operations.
Show an example of difference in syntax in Razor and WebForm View?
Razor @model.Message
Web Forms
Code expressions in Razor are always HTML encoded. This Web Forms syntax also automatically HTML encodes the value.
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.˝;
}
Web Forms
<%
int x = 123;
string y = “because.”;
%>
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, same can be achieved by checking requests header directly:
Request[“X-Requested-With”] == “XmlHttpRequest”.
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) {
Item @item.Name.
}
Web Forms
Item .
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.
How can you call a javascript function/method on the change of Dropdown List in MVC?
Create a java-script method:
function selectedIndexChanged() {
}
Invoke the method:
x.SelectedProduct,
new SelectList(Model.Users, “Value”, “Text”),
“Please Select a User”, new { id = “ddlUsers”,
onchange=”selectedIndexChanged()” })%>
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.

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.
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 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”;
}
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 fi le 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 fi le in the Views directory. It specifi es 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.
Note: Some of the content has been taken from various books/articles.
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)) {
}
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 specifi c 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:

  • This is all wrong!

 

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 specifi c 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.
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.
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);
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 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.
How do you return a partial view from controller?
return PartialView(options); //options could be Model or View name
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().
Conclusion:
I hope we covered a lot of questions to brush-up. Since MVC is very vast now,I know we have missed a lot stuff too.The content in the question and answer form is also taken from few renowned books like Professional asp.net MVC4 from wrox, and few of the content is taken from myMVC articles posted earlier.  My upcoming articles will provide interview questions for EntityFramework too.

 

Best of Luck and Happy Coding J.

Code First Approach using Entity Framework 4.1, Inversion of Control, Unity Framework, Repository & Unit of Work Pattern and MVC3 Razor View


Download Source Code

Introduction :
In my previous article I discussed about developing a simple basic multilayered architecture for a .Net application.However there were few points that I skipped considering that the article was for beginners.When we talk about an application architecture there are certain points that need to be put into consideration before initiating,
  • Is the architecture loosely coupled?
  • Is it to be service based?
  • Where should the entities reside?
  • What should be Mode of Communication with the database?
  • Do it require design patterns? If yes,What patterns should be implemented?
  • Should it be based on Seperation of Concerns?
To answer these type of questions, .Net 4 has come up with a generic solution,making use of Entity Framework.
My effort in this article would be to put some light on building a generic multilayered architecture using Entity Framework 4.1 and MVC3 razor view engine.We’ll use inversion of control to resolve dependency of layers.The points to be covered in this article would be as follows,
  • Use of Seperation of Concerns,
  • Use of Code First approach,
  • POCO objects,
  • Repository Pattern,
  • Dependency Injection and Inversion of Control.
Architecture Overview:
I have created an architecture to explaing all the above mentioned points, and we’ll stick to this architecture till the end of article thus implementing practically our understanding.
I have created a very simple application to add student details in database, To edit it and to delete it,My first page shows list of all added student.
The arcitecture is service based, following are the components and pictorial representation (fig1) of it, we’ll discuss each component in detail,
  1. CodeFirstData layer.
  2. CodeFirstEntities layer.
  3. CodeFirstServices layer.
  4. MVC Portal layer.


    Architecture components:

    Let’s discuss each and every component of the defined architecture in detail,
    1. CodeFirstData layer :
    The data layer is the class library defining a layer which is responsible for interacting with database, contains context classes and a factory pattern implementation to interact with database.The layer contains the repository for each entity to map with database,thus making a complete ORM (Object Resource Model) solution.The class library references EntityFramework dll to implement the dbcontext classes.
    1. CodeFirstEntities layer:
    Entity layer acts as a model to MVC application,and also responsible for creation of DataBase objects when the dbset is first executed.It contains Entity classes in POCO form, having relations and data annotations(Rules/Constraints to be put on Database table/columns).
    The properties of the class results in column name in database and name osf the class in Dtaabase table.Primary key is either defined by the property named Id or “Classname[Id]”,in our case “StudentId”,this is default protocol set by entityframework to keep in mind while creating entities.Since this application is codefirest,we need to create entities first.
    1. CodeFirstServices layer:
    The layer contains services which uses repositories to fetch data from database. The interaction between Services and Repositories is kept loosely coupled thus implementing Inversion of Control using Dependency Injection.Its constructor based dependency injection and do not allow service to make direct instance of our repositories.Service layer acts as an interface between controllers and repositories,passes request of controller to repositories.
    1. MVCPortal layer:
    MVCPortal layer is our UI layer, it contains Model/ViewModels,Views and Controllers.I am not going into details of MVC as its not our primary target,I assume that you already know how to create and run MVC application,Lets have a quick revision of MVC,
      1. Model / Viewmodel:
    Model classea are responsible for holding up and manipulating data,we bind model/viewmodel classes to views to display model specific data.model classes are prepopulated by controllers to show data with the lehp of views.
      1. Views :
    Views holds up our UI templates, We have controller methods defined for every view, which populates View Design with data, and requests particular type of view to be rendered at user’s end as per requirement.
      1. Controllers :
    Web-based MVC frameworks map URLs to server code in a bit different fashion. Instead of mapping incoming URLs to html/aspx files, they instead map URLs to methods on classes. These classes are called “Controllers” and they are responsible for processing incoming HTTP requests, handling user input, retrieving and saving data, and determining the response to send back to the client (display HTML, download a file, redirect to a different URL, etc.).
    The layer makes use of Dependency injection to achieve Inversion of Control for services, thus not allowing controllers to directly acces services instances,The IOC is acheived using global.asax file using UnityFramework library of Microsoft.
    5. Dlls : I have created DLLs folder and given the output build path for every class library to that folder, for ease of access to Dll’s to add reference.Now each Dll will be created in the Dlls folder and we can access the desired Dll from the same folder. Also keep the EntityFramework,UnityConfiguration Dlls into it.
    IOC and DI :
    Dependency Injection is an important component in my application . All the services are required to be late bound with Model layer with Dependency Injection. In addition, the IoC container manages the lifetime of service objects. For example the Context object. I set lifetime type as PerThreadLifetimeManager in Unity configuration. This makes one and only one context object created in a single request and the different request has a different context object. Another thing I want to mention is ASP.NET MVC3 has its own way to provide Dependency Inject for controller via implementing DependencyResolver interface. The IoC container I used in the demo is Unity.
    Container :
    The “Container” or “IOC Container” is the main object that is used to create objects and inject dependencies into them. Whenever you want an object to be open to IoC, you have to use the container to create the instance using container.Resolve() method instead of the “new” keyword.
    IService service = unityContainer.Resolve();
    I have added following references to acheive the same,
    Microsoft.Practices.Unity
    Microsoft.Practices.Unity.Configuration
    The code for IOC is implemented in global.asax file.
    Step by Step Process to create the Application using EntityFramework Architecture :
    Application Overview :
    We’ll try to develop a simple studentDetails application with the help of discusses architecture,The application’s main module will be to Create a new student, Edit existing student,Delete existing student, and to show list of all students.Looking into a wider/generic perspective, the application performs CRUD operations on database with the help of EF .
    Note that we’ll not create databse by our own,we just write classes and defing connection configuration of our database server in web.config file, and let EntityFramework do rest of the job of creating database, managing database and Mapping database with our entities.
    Step1. Creating a solution and blank projects/seperating them logically/physically as layers :
    Our first initiative is to prepare our initial level architecture there by creating solution and adding project files to it, We create a solution named CodeFirstEntities and add three class libraries to it thus defining our three layers which are Entity,Data and Service, the names of the class libraries which i chose are CodeFirstEntities,CodeFirstData and CodeFirstServices respectively.
    Now add an MVC3 application to the solution called MvcPortal, that will act as a UI layer for our application. Refer fig2 for implementing the first step.


                                                                       ( fig2 )

    Step 2. Creating Entities :
    Add Student.cs class to CodeFirstEntities project , this class will contain the student details specific properties that will take the shape of database table and columns . The class makes use of DataAnnotation dll to put data annotations (rules/constraints) over the properties that will be reflected in database table.The constraints like max length and required parameter are provided as attributes over the properties of the class as shown in fig3 and fig4,

                                                                                ( fig3 )

                                                                             ( fig4)
    The above entities is very simple POCO (Plain Old CLR Object) class and the entity Student is decorated with validation attributes in the System.ComponentModel.DataAnnotations namespace. Now we want to use these entities for defining model objects for the Entity Framework 4. Using the Code First approach of Entity Framework, we can first define the entities by simply writing POCO classes without any coupling with any API or database library. This approach lets you focus on domain model which will enable Domain-Driven Development for applications. EF code first support is currently enabled with a separate API that is runs on top of the Entity Framework 4.
    Step 3. Creating Repositories/Contexts :
    Our next step is to create the contexts/repositories for our application and classes that will interact with the database.
    A. Create Context Class for Entity Framework :
    We have already prepared our domain model now let’s create a class in order to working with Entity Framework Code First. I have added reference to EntitFramework.dll CTP 4.1 to this class library project. We create two folders DBInteractions and EntityRepositories to segregate our classes as in fig5, we’ll come to that later, first let me explain you the context class.
                                                                (fig 5)


                                                                                   (fig 6)

    The above class CodeFirstContext in fig 6 is derived from DbContext that can connect your model classes to a database. The CodeFirstContext class is mapping our Student class to
    database tables Student use DbSet where TEntity is any POCO class. When we arerunning the application at first time, it will automatically create the database. EF code-first look for a connection string in web.config or app.config that has the same name as the dbcontext class. If it is not find any connection string with the convention, it will automatically create database in local SQL Express database by default and the name of the database will be same name as the dbcontext class. You can also define the name of database in constructor of the the dbcontext class. The model classes of Code First are working on the basis of conventions and we can also use a fluent API to refine our model. The convention for primary key is ‘Id’ or ‘Id’ as I discussed before. If primary key properties are detected with type ‘int’, ‘long’ or ‘short’, they will automatically registered as identity columns in the database by default. Primary key detection is not case sensitive. We can define our model classes with validation attributes in the System.ComponentModel.DataAnnotations namespace and it automatically enforces validation rules when a model object is updated or saved.
    I ) DBInteractions :
    B. Generic Repository for EntityFramework Code First:
    We have now created model class and dbcontext class. Now we create a generic repository pattern for data persistence with EF code first. Let’s create a generic repository to working with DbContext and DbSet as follows,The following classes will be added to DBInteractions folder for ease of understanding logic.


                            
                                                                            (fig 7)

    1. DataBase Factory:
    We have our database factory class defined as follows,


                                                                (fig 8)

                                                                     (fig 9)
    Where IDBFactory is the interface implemented by our factory class DBFactory.The factory class is inherited from Disposable class as shown below in fig 10,Responsible for releasing disposing database resources.
    (fig 10)
    1. RepositoryBase – The Generic Entity Repository base class :


      Above is the repository base class that contains all the methods to be implemented for CRUD DB operations, we can define more of our generic methods here, for now considering our application, these are eough for proper understanding of the working.

      E. Unit of Work
      The Unit of Work pattern maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems.We create a class for handling Unit of Work pattern,
      Interface :


      Class :



      The Commit method written in of the UnitOfWork will call the commit method of our Context class and it will execute the SaveChanges method of DbContext class.

      II ) Repository :
      In this article, we will be primarily focus on the persistence against Student entity . Let’s create a repository for handling CRUD operations for Student
      using derive from a generic Repository EntityRepositoryBase.
      Repository class for Student :
      Interface :

      Class :

       

    Step 4. Creating a Service layer :
    Service Layer defines an application’s scope and its available set of operations from the perspective of interfacing client layers. It encapsulates the application’s business logic,
    controlling transactions and coordinating responses in the implementation of its operations. Controller classes should be made light and do not put much of business logic onto it. We can use
    the service layer as the business logic layer and can encapsulate the rules of the application.
    We define interfaces and corresponding student service for our application business logic,Since we are targetting CRUD operations, so the methods are quite simple in implementation,
    Interface :

     
    As we can see in abve interface the methods are to Get Student Details,List,Update and Delete Student.
    Class :
    usingSystem.Collections.Generic;
    usingCodeFirstData.DBInteractions;
    usingCodeFirstData.EntityRepositories;
    usingCodeFirstEntities;
    usingCodeFirstServices.Interfaces;
    namespaceCodeFirstServices.Services
    {
    publicclassStudentService: IStudentService
    {
    privatereadonlyIStudentRepository_studentRepository;
    privatereadonlyIUnitOfWork_unitOfWork;
    publicStudentService(IStudentRepositorystudentRepository, IUnitOfWorkunitOfWork)
    {
    this._studentRepository = studentRepository;
    this._unitOfWork = unitOfWork;
    }
    #regionIStudentService Members
    publicIEnumerable<Student> GetStudents()
    {
    varstudents = _studentRepository.GetAll();
    returnstudents;
    }
    publicStudentGetStudentById(intid)
    {
    varstudent = _studentRepository.GetById(id);
    returnstudent;
    }
    publicvoidCreateStudent(Studentstudent)
    {
    _studentRepository.Add(student);
    _unitOfWork.Commit();
    }
    publicvoidDeleteStudent(intid)
    {
    varstudent = _studentRepository.GetById(id);
    _studentRepository.Delete(student);
    _unitOfWork.Commit();
    }
    publicvoidUpdateStudent(Studentstudent)
    {
    _studentRepository.Update(student);
    _unitOfWork.Commit();
    }
    publicvoidSaveStudent()
    {
    _unitOfWork.Commit();
    }
    #endregion
    }
    }
    Class uses refernces of Repositories and Entities, and Dependency of Repositories is resolved in Constructor of the service itself.
    Step 5. The MVC Portal :
    Before we start MVC portal,Lets clear our logic for IOC and DI.I have already discussed IOC in the article.For resolving Dependency we create certain classes as discussed below, to get independent service request,
    We also create a custom lifetime manager for Unity to store container in the current HttpContext.
    publicclassHttpContextLifetimeManager : LifetimeManager, IDisposable
    {
    publicoverrideobjectGetValue()
    {
    varassemblyQualifiedName = typeof(T).AssemblyQualifiedName;
    if(assemblyQualifiedName != null)
    returnHttpContext.Current.Items[assemblyQualifiedName];
    returnnull;
    }
    publicoverridevoidRemoveValue()
    {
    varassemblyQualifiedName = typeof(T).AssemblyQualifiedName;
    if(assemblyQualifiedName != null)
    HttpContext.Current.Items.Remove(assemblyQualifiedName);
    }
    publicoverridevoidSetValue(objectnewValue)
    {
    varassemblyQualifiedName = typeof(T).AssemblyQualifiedName;
    if(assemblyQualifiedName != null)
    HttpContext.Current.Items[assemblyQualifiedName] = newValue;
    }
    publicvoidDispose()
    {
    RemoveValue();
    }
    }
    }
    We create a dependency resolver for resolving service dependency as follows,
    ASP.NET MVC 3 has introduced a new interface IControllerActivator which lets you activate controllers with custom behavior and can be use it for dependency injection purpose.The
    IControllerActivator interface is discoverable using the dependency resolver. Let’s create a custom controller activator class by deriving from IControllerActivator intreface
    usingSystem;
    usingSystem.Web.Mvc;
    namespaceCodeFirstPortal.IoC
    {
    publicclassCustomControllerActivator: IControllerActivator
    {
    IControllerIControllerActivator.Create(
    System.Web.Routing.RequestContextrequestContext,
    TypecontrollerType){
    returnDependencyResolver.Current
    .GetService(controllerType) asIController;
    }
    }
    }
    We also create a UnityController Factory and Configure contract and concrete types of unity in global.asax file.
    ASP.NET MVC 3 has also introduced a new interface IDependencyResolver which exposes two methods – GetService and GetServices.The GetService method resolves singly registered services
    that support arbitrary object creation and the GetServices resolves multiply registered services. Implementations of the IDependencyResolver interface should delegate to the underlying
    dependency injection container to provide the registered service for the requested type. When there are no registered services of the requested type, the ASP.NET MVC framework expects
    implementations of this interface to return null from GetService and to return an empty collection from GetServices. Let’s create a custom dependency resolver class by deriving from
    IDependencyResolver intreface in order to working with Unity to providing dependency injection.
    usingSystem;
    usingSystem.Web;
    usingSystem.Web.Mvc;
    usingSystem.Web.Routing;
    usingMicrosoft.Practices.Unity;
    namespaceCodeFirstPortal.IoC
    {
    publicclassUnityControllerFactory: DefaultControllerFactory
    {
    IUnityContainercontainer;
    publicUnityControllerFactory(IUnityContainercontainer)
    {
    this.container = container;
    }
    protectedoverrideIControllerGetControllerInstance(RequestContextreqContext, TypecontrollerType)
    {
    IControllercontroller;
    if(controllerType == null)
    thrownewHttpException(
    404, String.Format(
    “The controller for ‘{0}‘ could not be found”+ “or it does not implement IController.”,
    reqContext.HttpContext.Request.Path));
    if(!typeof(IController).IsAssignableFrom(controllerType))
    thrownewArgumentException(
    string.Format(
    “Requested type is not a controller: {0},
    controllerType.Name),
    “controllerType”);
    try
    {
    controller= container.Resolve(controllerType) asIController;
    }
    catch(Exceptionex)
    {
    thrownewInvalidOperationException(String.Format(
    “Error resolving the controller {0},
    controllerType.Name), ex);
    }
    returncontroller;
    }
    }
    Resolving Service Dependency :
    usingSystem;
    usingSystem.Collections.Generic;
    usingSystem.Web.Mvc;
    usingMicrosoft.Practices.Unity;
    namespaceCodeFirstPortal.IoC
    {
    publicclassUnityDependencyResolver: IDependencyResolver
    {
    IUnityContainercontainer;
    publicUnityDependencyResolver(IUnityContainercontainer)
    {
    this.container = container;
    }
    publicobjectGetService(TypeserviceType)
    {
    try
    {
    returncontainer.Resolve(serviceType);
    }
    catch
    {
    returnnull;
    }
    }
    publicIEnumerable<object> GetServices(TypeserviceType)
    {
    try
    {
    returncontainer.ResolveAll(serviceType);
    }
    catch
    {
    returnnewList<object>();
    }
    }
    }
    }
    global.asax :
    Add service project reference , entity project reference and data project reference to the portal.
    The SetResolver method of DependencyResolver class provides a registration point for dependency injection containers. In this method, we configure the UnityDependencyResolver class for
    providing dependency injection with Unity 2.0. The SetResolver method will be working with any dependency injection container.If you want to use StructureMap as the dependency injection
    container, you can create a dependency resolver class in order to working with StructureMap by deriving IDependencyResolver intreface and later you can configure this class with SetResolver
    method. The ASP.NET MVC 3 is providing a good support for working with dependency injection containers.
    usingSystem.Web.Mvc;
    usingSystem.Web.Routing;
    usingCodeFirstData.DBInteractions;
    usingCodeFirstData.EntityRepositories;
    usingCodeFirstPortal.IoC;
    usingCodeFirstServices.Interfaces;
    usingCodeFirstServices.Services;
    usingMicrosoft.Practices.Unity;
    namespaceMvcPortal
    {
    publicclassMvcApplication: System.Web.HttpApplication
    {
    publicstaticvoidRegisterGlobalFilters(GlobalFilterCollectionfilters)
    {
    filters.Add(newHandleErrorAttribute());
    }
    publicstaticvoidRegisterRoutes(RouteCollectionroutes)
    {
    routes.IgnoreRoute(“{resource}.axd/{*pathInfo}”);
    routes.MapRoute(
    “Default”, // Route name
    “{controller}/{action}/{id}”, // URL with parameters
    new{ controller = “Home”, action = “Index”, id = UrlParameter.Optional } // Parameter defaults
    );
    }
    protectedvoidApplication_Start()
    {
    AreaRegistration.RegisterAllAreas();
    RegisterGlobalFilters(GlobalFilters.Filters);
    RegisterRoutes(RouteTable.Routes);
    IUnityContainercontainer = GetUnityContainer();
    DependencyResolver.SetResolver(newUnityDependencyResolver(container));
    }
    privateIUnityContainerGetUnityContainer()
    {
    //Create UnityContainer
    IUnityContainercontainer = newUnityContainer()
    .RegisterType<IDBFactory, DBFactory>(newHttpContextLifetimeManager<IDBFactory>())
    .RegisterType<IUnitOfWork, UnitOfWork>(newHttpContextLifetimeManager<IUnitOfWork>())
    .RegisterType<IStudentService, StudentService>(newHttpContextLifetimeManager<IStudentService>())
    .RegisterType<IStudentRepository, StudentRepository>(newHttpContextLifetimeManager<IStudentRepository>());
    returncontainer;
    }
    }
    }
    To Start with MVC our first step is to define our connection string as follows in the web.config file.
    Steps to Create Controllers and Views :
    1. We start with home Controller, as it is the default controller set in global.asax to be called first.
      When the Index action of the controller is called we redirect it to our Student Controller,which straight away returns view to show listy of students if exist,since its first time we are creating the controller,it shows an empty list, the controller method of Student fetches student list from database , but first it creates the database, thus acheiving our objective.
    1. We create Student Controller, We define actions in the controller for each operation we want to perform as follows,
    usingSystem;
    usingSystem.Linq;
    usingSystem.Web.Mvc;
    usingCodeFirstEntities;
    usingCodeFirstServices.Interfaces;
    namespaceCodeFirstPortal.Controllers
    {
    publicclassStudentController: Controller
    {
    privatereadonlyIStudentService_studentService;
    publicStudentController(IStudentServicestudentService)
    {
    this._studentService = studentService;
    }
    [HttpGet]
    publicActionResultDetails(int? id)
    {
    varstudentDetails = _studentService.GetStudentById((int) id);
    if(studentDetails == null) thrownewArgumentNullException(“Not Found”);
    returnView(studentDetails);
    }
    [HttpGet]
    publicActionResultDelete(int? id)
    {
    varstudentDetails = _studentService.GetStudentById((int) id);
    if(studentDetails == null) thrownewArgumentNullException(“Not Found”);
    returnView(studentDetails);
    }
    [HttpPost]
    publicActionResultDelete(Studentstudent)
    {
    _studentService.DeleteStudent(student.StudentId);
    returnRedirectToAction(“List”, “Student”);
    }
    [HttpGet]
    publicActionResultEdit(int? id)
    {
    varstudentDetails = _studentService.GetStudentById((int) id);
    if(studentDetails == null) thrownewArgumentNullException(“Not Found”);
    returnView(studentDetails);
    }
    [HttpPost]
    publicActionResultEdit(Studentstudent)
    {
    _studentService.UpdateStudent(student);
    returnRedirectToAction(“List”, “Student”);
    }
    [HttpGet]
    publicActionResultCreate()
    {
    returnView();
    }
    [HttpPost]
    publicActionResultCreate(Studentstudent)
    {
    varstudentModel = newStudent()
    {
    Address = student.Address,
    Country = student.Country,
    Name = student.Name,
    Age = student.Age,
    Email = student.Email
    };
    _studentService.CreateStudent(studentModel);
    returnRedirectToAction(“List”, “Student”);
    }
    [HttpGet]
    publicActionResultList()
    {
    varstudents = _studentService.GetStudents();
    if(students.Any())
    {
    returnView(“List”, students);
    }
    returnView(“List”);
    }
    }
    }
    There are get and corresponding Posts for each method responsible for Data Updations. The Constructor of the controller initializes the Service,we can see it do not create direct instance.
    1. We Create Views for every Action,Its easy if we right click the controller action and create view,It automatically create a view with a Default folder named in the name of Constructor,So we can create all the views for our operations, and our solution looks like,
      4. Now we are ready with our application to be executed,keep your fingers crossed and see the magic, I have used _layout as master page to give some meaningful look and feel to my application,U can customize the same.When u run the application by pressing F5, We get redirected to the Index view of Student Controller,which shows list of students,since we are running it first time,we dont have existing list, and our application shows,



      1. No wonder , just have a look at your DataBase, My case I am using Sql Server 2008,


        I got a Database created automativcally with the name CodeFirstApp having Student Table, Now you can cross verify the table with your entity,its the same.So we have hit the target and our database is successfully created.

        1. Further Operations :
        You can now test the application and perform further CRUD operations in the application and see the DataBase getting updated.e.g. Create Student,


        after Submit by pressing Create, we get,


        therefore one student created.

        We can edit the same student by pressing edit link , we get the view,


        Likewise we can see the details of already created student,


        and delete the student will redirect to ,


        I had created 3 students in the same manner, You can create more and play with the application.

        Risk Factor : There is also a Risk Factor in implementing EntityFramework, If we do any change in the entity, like deleting,changing property,The context will drop and recreate the database, which may clearly lead to loss of your existing data.To avoid this critical situation, we code some more, we call SetInitializer method of DataBase class and set it to null in our dataBase Factory Class.

        usingSystem.Data.Entity;
        namespaceCodeFirstData.DBInteractions
        {
        publicclassDBFactory: Disposable, IDBFactory
        {
        publicDBFactory()
        {
        Database.SetInitializer<CodeFirstContext>(null);
        }
        privateCodeFirstContextdataContext;
        publicCodeFirstContextGet()
        {
        returndataContext ?? (dataContext = newCodeFirstContext());
        }
        protectedoverridevoidDisposeCore()
        {
        if(dataContext != null)
        dataContext.Dispose();
        }
        }
        }
        Database class is from namespace System.Data.Entity, whcih provides such feature.
        Conclusion :
        In this article we discussed about creating an application using EntityFramework 4.1 Code First Approach, We used Inversion of control and Dependency Injection to Resolve Dependency between layers.We used MVC 3 razor view engine as our UI and integrated the layers to acheive our objective.The application was a description of simple CRUD operations on Database.We learned how to use Repository Pattern,Unit of Work pattern and Unity Framework.You can download the codebase and further enhance/extend it according to your need.Happy Coding.

        Articles : http://www.codeproject.com/script/Articles/BlogFeedList.aspx?amid=7869570