Code-First Flow Demo of creation of database and tables
In Code-First flow, the database is not created, but the models (classes) are created first. These models will be transformed into tables.
The below-detailed steps will help you to create a Code-First database:
a. Create a new project in Visual Studio 2019, and select the 'ASP .Net Web Application' template.
b. Provide a name and click 'Create'.
d. Add a .cs file to the project - CodeFirstDemo.cs
e. Copy and paste the below code -
A domain Subject can have many Tags, and Tags can be tagged to many Subjects. Hence, it has many-to-many relationship. However, a Subject can have one Author (just an assumption) and once SubjectField.
public class Subject
{
public int Id { get; set; }
public string Title { get; set; }
public string Description { get; set; }
public SubjectField Field { get; set; }
public float Price { get; set; }
public Author Author { get; set; }
public IList<Tag> Tags { get; set; }
}
public class Author
{
public int Id { get; set; }
public string Name { get; set; }
public IList<Subject> Subjects { get; set; }
}
public class Tag
{
public int Id { get; set; }
public string Name { get; set; }
public IList<Subject> Subjects { get; set; }
}
public enum SubjectField
{
Engineering = 1,
Medical = 2,
Commerce = 3
}
f. Next, we need to install 'Entity Framework' NuGet package.Navigate to Tools->Nuget Package Manager->Manage Nuget package for solutions. Search for Entity Framework. Select Entity Framework 6. Click o Install. This will install Entity Framework.
g. Next, add below code. DbContextclass is defined in using System.Data.Entity; We need to create a class which overrides DbContext. This class should have DbSet. DbSet is a collections of objects which represent the tables in the Database.
public class BookDbContext : DbContext
{
public DbSet<Subject> Subjects { get; set; }
public DbSet<Author> Authors { get; set; }
public DbSet<Tag> Tags { get; set; }
public BookDbContext()
: base("name=DefaultConnection")
{
}
}
h. We have created domains, and DbContext class. Next, we should create connection string; connection string is required to tell the EF which DB engine to use. We can use any DB engine: AWS aurora, AQL server etc. That's the beauty of EF.
To provide a connection string in the config file, open appsettings.json and provide below code:
The connection string is Server=localhost;Database=vul_master;Trusted_Connection=True
public BookDbContext()
: base("Server=localhost;Database=vul_master;Trusted_Connection=True")
{
}
i. We have created domains, then DBConext class and also provided the connection string details. Now, we need to enable the migrations; this is a one-time task.
To enable the migrations, we need to open Packgae Manager console.
Opne Package Manager Console, and run the below command:
enable-migrations
A Migration folder would have been created.
j. A migration folder has been created. Now, we need to add a migration and update the database; this will create the tables in the database.
To add a migration, run below command:
add-migration <name of the migration>
After this, update the database by running following command:
update-database
k. To check the database and the tables, open Microsft SQL server management studio and select localhost
l. Expand the database you would have provided in the connection string; then expand the tables. You would see the tables.
Code is available here- https://github.com/bharath9788/CodeFirstDemo.git
