With a complete data model, we can generate the database file. I use Entity Designer Database Generation Power Pack as it helps when you update the entity model and then have to regenerate the database file and data classes. And that covers part two.
In this part we took the data model created using Entity Framework in the first part and generated a. We then took that file and used SQLMetal to generate data classes for us. Then we added that to our Windows Phone project and fixed all the errors to make it compatible. Next part will cover using these generated classes to create a database in Isolated Storage on the handset and populate it with default data. I do like Entity Framework for other project types so it was simple to apply something I already know.
Honesty, it takes me no time at all creating the data model in EF, under 30 min for projects like the one described here. Some Important points to note here are: Code-first will create a table in the database. It will also create other columns with the same name and datatype as property names as shown in the following screenshot. View All. Entity Framework Code First Example. Prashant Shinde Updated date Dec 28, So, in this article, we will learn how to develop a simple C application using the Entity Framework code-first approach.
Add a new console application project named "CodeFirstConsole" to this solution so that we can test these classes:. Set "CodeFirstConsole" as the startup project. Next Recommended Reading. Net Core 6. An Enrollment entity is associated with one Student entity, so the property can only hold a single Student entity unlike the Student.
Enrollments navigation property you saw earlier, which can hold multiple Enrollment entities. The CourseID property is a foreign key, and the corresponding navigation property is Course. An Enrollment entity is associated with one Course entity. In the Models folder, create Course. A Course entity can be related to any number of Enrollment entities.
We'll say more about the DatabaseGeneratedAttribute attribute in a later tutorial in this series. Basically, this attribute lets you enter the primary key for the course rather than having the database generate it.
The main class that coordinates Entity Framework functionality for a given data model is the database context class. You create this class by deriving from the System. DbContext class. In your code, you specify which entities are included in the data model. You can also customize certain Entity Framework behavior.
In this project, the class is named SchoolContext. To create a folder in the ContosoUniversity project, right-click the project in Solution Explorer and click Add , and then click New Folder. In that folder, create a new class file named SchoolContext. This code creates a DbSet property for each entity set. In Entity Framework terminology, an entity set typically corresponds to a database table, and an entity corresponds to a row in the table. Entity Framework would include them implicitly because the Student entity references the Enrollment entity and the Enrollment entity references the Course entity.
The name of the connection string which you'll add to the Web. You could also pass in the connection string itself instead of the name of one that is stored in the Web. For more information about options for specifying the database to use, see Connection strings and models. If you don't specify a connection string or the name of one explicitly, Entity Framework assumes that the connection string name is the same as the class name. The default connection string name in this example would then be SchoolContext , the same as what you're specifying explicitly.
The modelBuilder. Remove statement in the OnModelCreating method prevents table names from being pluralized. If you didn't do this, the generated tables in the database would be named Students , Courses , and Enrollments. Instead, the table names will be Student , Course , and Enrollment.
Developers disagree about whether table names should be pluralized or not. This tutorial uses the singular form, but the important point is that you can select whichever form you prefer by including or omitting this line of code.
Entity Framework can automatically create or drop and re-create a database for you when the application runs. You can specify that this should be done every time your application runs or only when the model is out of sync with the existing database. You can also write a Seed method that Entity Framework automatically calls after creating the database in order to populate it with test data.
The default behavior is to create a database only if it doesn't exist and throw an exception if the model has changed and the database already exists. In this section, you'll specify that the database should be dropped and re-created whenever the model changes. Dropping the database causes the loss of all your data. This is generally okay during development, because the Seed method will run when the database is re-created and will re-create your test data.
But in production you generally don't want to lose all your data every time you need to change the database schema. Later you'll see how to handle model changes by using Code First Migrations to change the database schema instead of dropping and re-creating the database.
The Seed method takes the database context object as an input parameter, and the code in the method uses that object to add new entities to the database. For each entity type, the code creates a collection of new entities, adds them to the appropriate DbSet property, and then saves the changes to the database. It isn't necessary to call the SaveChanges method after each group of entities, as is done here, but doing that helps you locate the source of a problem if an exception occurs while the code is writing to the database.
To tell Entity Framework to use your initializer class, add an element to the entityFramework element in the application Web. The context type specifies the fully qualified context class name and the assembly it's in, and the databaseinitializer type specifies the fully qualified name of the initializer class and the assembly it's in.
For more information, see Configuration File Settings. An alternative to setting the initializer in the Web. The application is now set up so that when you access the database for the first time in a given run of the application, Entity Framework compares the database to the model your SchoolContext and entity classes.
If there's a difference, the application drops and re-creates the database. When you deploy an application to a production web server, you must remove or disable code that drops and re-creates the database. You'll do that in a later tutorial in this series. It's easy to install and configure, starts on demand, and runs in user mode. LocalDB is installed by default with Visual Studio.
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