Entity Framework 5 Code First in MVC 4 for beginners

Transcription

1 Entity Framework 5 Code First in MVC 4 for beginners A database can be created using Code First approach in Entity Framework 5. We will create a simple application that will save recipe of dishes and information of writer of recipe. Its demo application is linked at the end which will help to things understand the concept easily. First, we should understand what Entity Framework is. Database First The first iteration of Entity Framework, which came as part of.net 3.5 and VisualStudio 2008, enables developers to create this model by reverse engineering an existing database into an XML file. The XML ends with the EDMX extension which can be viewed with a designer, and it can be customized to better suit your domain. Model First With the release of Visual Studio 2010 and.net 4, the second version of Entity Framework was also released. This version, called Entity Framework 4, aligned it with the.net version. A new feature that was added was Model First. Model First enabled you to design conceptual model in the visual designer which enabled database creation based on the model. Model First allows developers working on new projects that do not have legacy databases to benefit too. Developers can develop the application domain by designing the conceptual model. The database is created from that process. Database First and Model First After you have designed the EDMX, you should let automatic code generation build classes based on the entities and their relationships. Developers can use them to represent domain objects. EF4. In.NET 3.5 and POCO Another critical change came in EF4. In.NET 3.5, the only way Entity Framework was able to manage inmemory objects was by requiring classes to inherit from Entity Object. This enabled the database to track the changes made. POCO (Plain Old CLR Object) was also introduced which enabled the Entity Framework to track changes to simpler classes without needing the Entity Object. This benefited developers as it allowed them to develop classes and use them. Code First Code First is a modeling path that lets the code define the domain model. This is beneficial for developers since they are at ease writing codes rather than using a designer. Developers can define the domain model through POCO.

2 With this approach you don t need to do anything with SQL Server because Code First is designed to create database purely from POCO classes. In Code First technique, models represent our tables in database and properties represent columns in table Note: We will work with two POCO classes so that we can focus on understanding of creation of database. We will make a change in our model, and then will see how to update database again to match our updated model. In this tutorial we will discuss: Creation of domain model using POCO classes Creation of database according to classes Scaffold the CRUD operators Change in Model and Updating Database Before proceeding, I want to make some terms easier for you like Scaffolding. Scaffolding is new feature introduced to create views and controller automatically. It is used to automatically generate the baseline of your application's CRUD (Create, Read, Update and Delete) without writing a single line of code. If you have not written any MVC application till now, don t worry since after this tutorial you will be able to perform basic CRUD operations in MVC using Entity Framework 5 Code First. So let s start our tutorial by understanding database structure. This is One to Many relationship which shows Writers may have written many Recipes but One Recipe is only and only written by one Writer

3 Creating MVC 4 Project : Open your Visual Studio > click on File -> New -> Project

4 Select Visual C# in left pane, and then select ASP.NET MVC 4 Web Application and name it KitchenApp And click Ok as shown in picture

5 In the next dialog box, select Empty Project Template, and I will add things manually that will help you to understand project in better way. Then select Razor in View engine drop down because it is recommended to use Razor engine and click Ok. This will create project with some basic files and folders that we will use further in our tutorial.

6 Now your Project solution should look like

7 According to our project, we need two Entities. First Writer will hold information regarding Writer and we also need Recipe for Recipe information. In MVC, we have basic structure of project which tells us that operations related Models should be done in Model folder. Model folder will contain all model classes like Writer and Recipe. Views folder will contain pages that will be shown to user. Controllers folder will have Action method that will coordinate with models and Views. This will help us to easily maintain UI pages separate and Model and Controllers logic separately Let s add Model class Writer in Models Folder. To add class, right click on Models folder and then Add New Item. This will open dialog box.

8 Expand Visual C#, and select Code from left pane. Then select Class and name is Writer.cs, and click Add button.

9 This will add a class Writer in Models folder and repeat this step to add Recipe.cs class After this, the Solution Explorer should have both these files added - Double click on Writer.cs, and add following code in this class publicclasswriter { publicint Id { get; set; } [Required] publicstring Name { get; set; } publicvirtualicollection<recipe> Recipes { get; set; } } This code shows Id that will be used as primary key in our database table. Entity Framework identifies itself property that should be primary key by searching Id in property or Class Name ending with Id, compiler will search for this sequence of character in class and will make it primary key. Name property will be Name column and [Required] shows Name is required and this column can t be null in table. Note that [Required] will show you error because they reside in System.ComponentModel.DataAnnotations name space to use Annotation tags you just need to add following name space usingsystem.componentmodel.dataannotations;

10 As we know that one writer can have multiple Recipes, that s why ICollection has been added. It will tell SQL Server relationship between Writer and Recipe Table. Recipes property will hold list of Recipes this means Writer may have many Recipes associated with Writer. Now double click on Recipe.cs and add following code in Recipe.cs class publicclassrecipe { publicint Id { get; set; } [Required] publicstring Content { get; set; } publicintwriterid { get; set; } publicvirtualwriterwriter { get; set; } } Here Id will become Id of Recipe table, and it will be auto incremented. Then we have Content that will hold formula of our recipe, and WriterId will be foreign key references to Id of Writer and in last publicvirtualwriterwriter { get; set; } This property will show that Recipe will have only one Writer associated with one Recipe. Up to here, both your classes should look like Writer.cs

11 Recipe.cs

12 Now we need to configure our project for Entity Framework 5.0. To configure our project for Entity Framework 5.0 we need to install Entity Framework 5.0. The steps to install Entity Framework 5.0 are as follows. Click on Tools -> Library Package Manager and click on Package Manager Console this will open panel at bottom of Visual Studio 2012

13 Here is snap shot

14 Now to install Entity Framework 5.0, you just need to write following command PM> Install-Package EntityFramework -version You will see confirmation after few seconds till Visual Studio 2012 downloads and installs Entity Framework 5.0 for your project It will also add some code in web.config which is at root in solution explorer Now let s write a simple class that will inherit from DbContext class The DbContext class is responsible for interacting with data as objects is System.Data.Entity.DbContext. This class will be responsible for interacting with our Database for creating database, creating tables, and for all CRUD operations. It will also connect to database, and there will be no need to initialize any SqlConnection, SqlAdapter or anything else like we do traditionally in SqlClient

15 Adding Context Class Add a simple class as we added model in previous steps To add class, Right click on Models folder in solution explorer and New Item this will open dialog box, name your class as KitchenContext After creating this class, add the following name space in the class usingsystem.data.entity; Then paste the following code. Your class should look like (Must inherit your class with DbContext) publicclasskitchencontext : DbContext { publicdbset<writer> Writers { get; set; } publicdbset<recipe> Recipes { get; set; } } Here KitchenContext class is inherited from DbContext class to get Entity Framework functionalities. There are two properties in this class publicdbset<writer> Writers { get; set; }

16 This property shows that we need table of Writer model and its table name will be Writers and same for other property. PART 1 We can get all writers in table by making object of KitchenContext class that will perform all transactions with database. We will cover this code in further tutorial also. privatekitchencontextdb = newkitchencontext(); db.writers.tolist(); Above two lines of code will return list of writers. So up to here we have now created kitchencontext class and class should look like Now, let s focus on Entity Frame work. We will tell it where to create our database and what should be the name of database by putting Connection String in web.config file. The actual database can be generated without mentioning connection string, and the name of database will be same as context class. Its good practice to mention connection string so that we can name our database manually and we can modify user of database. To do this, open web.config file from solution explorer and add connection string next to ConfigSections tag. In our case, the connection string for data base is as follows <connectionstrings> <addname="kitchencontext"connectionstring="data Source=DOTNET-PC\MSSQLSERVER2K8;Initial Catalog=KitchenDB;User ID=sa;Password=1234"providerName="System.Data.SqlClient"/> </connectionstrings>

17 Name of connection string should be same as context class name. In our case, name is KitchenContext, and you need to change source according to your pc. Catalog=KitchenDB will be name of database, but you can give any name. In our case, ID=sa and password is 1234 but you need to change it according to your SQL server setting. Your web.config should look like We have completed all the required tasks for making our database.

18 Creating Database with Migration Migration will help us to update our database with our models if the models are changed Click on Tools -> Library Package Manager and click on Package Manager Console. This will open panel at bottom of Visual Studio 2012 And execute command PM> Enable-Migrations You will get confirmation as below

19 This will add Migrations folder in solution explorer that contains one class named as Configurations.cs

20 Well this class is very simple, this is default code written when class is created after executing command You need to make AutomaticMigrationsEnabled = true so that you can update database easily otherwise you will need to do additional steps to update database. AutomaticMigrationsEnabled = true is better when you don t want to track information of changing of database otherwise it is recommended to use AutomaticMigrationsEnabled = false. Seed method is automatically invoked after creation of database. This method is used to insert some test data in database in our case we will add data from our pages

21 To create database, you all need to do PM> Update-Database This means database is created;now open SQL server to confirm our database has been created Note that the name of Database is same which was mentioned in connection string, and name of tables same as properties created in KitchenContext.cs And column names are same as properties created in Writer.cs and Recipe.cs

22 Creating Controllers and Views using Scaffolding option With the help of Scaffolding, you can create Controller and views with basic CRUD operations without writing single line of code. To add Controller, right click on Controllers folder, then add, and then click on Controller.

23 The following dialog box will open Note: If you don t get Template MVC Controller with read/write actions and views using Entity Frame work, then please check for ASP.NET MVC Tools Update

24 We are adding controller for Writer model with the name WriterController. Select Template, select model class, and in the last DataContext class that s KitchenContext. Click Add, and this will add controller with basic code for CRUD operations and also views.

25 Repeat this step and add Controller for Recipe

26 Updated solution explorer looks like

27 You need to remove some automatic generated code from Create.cshtml and Edit.cshtml at bottom of page Change it to

28 Do this for all Create and Edit pages, and your application is ready. Press control+f5 to execute and navigate to writer like this You don t need to change your port number, in my case it s Create Writer by clicking on Create New link.

29 Now add the ActionLink code at the bottom of Index.cshtml in solution explorer -> View -> Writer -> First parameter: Text to display Second parameter: Which action to redirect Third parameter: Name of Controller where action is present

30 To navigate from Recipe/Index to Writer/Index add the highlighted code after </table> Now Click on

31 Create New Recipe Here you can see Writer that was added earlier. In this drop down we will have all writers

32 Even you don t need to apply validation because Scaffolding has applied for your Changing Model and updating Database: Now I am going to add Title property in Recipe.cs to add Title column in Recipes Table

33 To update your database you need to run Update-Database Command again in Package Manager Console This will update your database according to your changed model Now you can manually add this field in your page or you can delete RecipeController and Recipe folder in Views, and add RecipeController again. In my case I am adding controller again by deleting previous created RecipeController and Recipe folder in Views. Make sure you have deleted previous RecipeControll and its views.

34 Click add and repeat this previous step for removing some auto generated code increate.cshtml and Edit.cshtml

35 Then add link for Writers List Again run your application by Control +F5 and navigate to writer like this You don t need to change your port number, in my case it s 1999.

36 Title field is added and [Required] validation is also applied Note: To view validation messages click on Create button without filling form with data