What is Code First approach in Entity Framework?

The Code-First approach in Entity Framework (EF) is one of the three main approaches used to create and work with the Entity Data Model (EDM), which represents the conceptual model of an application’s domain and how it relates to the underlying database. In the Code-First approach, the emphasis is on defining the domain model classes and their relationships in code, without the need for a pre-existing database schema.

Here’s how the Code-First approach works:

  1. Define Domain Model Classes (Entities): Developers start by writing plain C# or VB.NET classes to represent the entities and their properties. These classes are typically referred to as POCOs (Plain Old CLR Objects). Each entity class represents a table in the database, and each property of the entity represents a column in the table.For example, consider a simple Product entity class:
public class Product
{
    public int ProductId { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}
  1. Create DbContext Class: The DbContext class is a key component in the Code-First approach. It represents a session with the database and provides a connection point to query and interact with the database. Developers define a class that inherits from DbContext, and this class contains properties representing the DbSet for each entity in the domain model.
public class AppDbContext : DbContext
{
    public DbSet<Product> Products { get; set; }
}
  1. Configure DbContext and Connection String: Developers also configure the DbContext class and connection string through configuration files or code, indicating which database provider to use and the connection details.
  2. Database Initialization and Migrations: Once the domain model classes and DbContext are defined, Entity Framework can create the corresponding database schema automatically based on these classes. This process is known as database initialization. When the application starts, Entity Framework checks if the database exists and, if not, it creates the necessary tables based on the entity classes.As the application evolves and the domain model changes, Entity Framework supports database migrations, which are code-based updates to the database schema. Migrations help manage changes to the database while preserving existing data.

The Code-First approach is well-suited for greenfield projects, where the database is built from scratch and developers have more control over the domain model. It allows developers to work with a rich object-oriented model without the need to design the database schema first. Code-First provides flexibility and ease of use, making it a popular choice for many modern applications developed using Entity Framework.

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