What approaches exist within the EF Core ecosystem?

Within the Entity Framework Core ecosystem, there are three main approaches for working with the database schema:

1. Database First: The database schema already exists, and EF Core generates model classes (entities) and DbContext based on this schema.

   • Advantages: Quick start when a database is ready, schema is fully controlled by the database.
   • Disadvantages: Changes in the database require re-generating code, which can overwrite customized code.

   // Example command for generating from an existing database
   // Scaffold-DbContext "Server=(localdb)\\mssqllocaldb;Database=MyDatabase;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models
   

2. Code First: You define models (entities) and DbContext in C# code. EF Core creates or updates the database schema based on these definitions using migrations.

   • Advantages: Full control over model code, integration with application codebase, use of migrations to manage schema changes.
   • Disadvantages: Requires migration management, schema changes always start with code modifications.

   // Example model class in Code First approach
   public class Product
   {
       public int Id { get; set; }
       public string Name { get; set; }
       public decimal Price { get; set; }
   }
   

3. Model First: Although historically present in older EF versions (pre-Core), in EF Core it is not native or standalone in the same sense as Database First or Code First. Essentially, Model First in EF Core reduces to writing models in code (like in Code First) and then generating the database from them. There is no separate visual model designer as in EF 6. Therefore, in EF Core, it is often considered a special case of Code First, where you manually describe the model without using an existing database.

Main characteristics of the approaches:

Approach	Starting point	Database schema management	Tools for changes
Database First	Existing database	Manually in the database	Scaffold-DbContext
Code First	Model classes and DbContext in C#	EF Core migrations	Add-Migration, Update-Database
Model First (in EF Core context)	Model classes and DbContext in C# (without existing database)	EF Core migrations or generation at runtime	Add-Migration, Update-Database

The choice of approach depends on the initial project conditions and team preferences. Code First is the most common approach in new EF Core projects due to its flexibility and integration with the development process.