Entity Framework Core

Entity Framework Core (EF Core) is a modern, cross-platform, extensible object-relational mapper (ORM) for .NET. It enables .NET developers to work with a database using .NET objects that map to the database tables. It eliminates the need for most of the data-access code that developers typically need to write.

What is Entity Framework Core?

EF Core provides a set of APIs for:

• Defining a data model: You can define your database schema using .NET classes and attributes, or by using code-first conventions.
• Querying data: EF Core translates LINQ queries into SQL queries that are executed against the database.
• Saving data: You can add, update, and delete entities, and EF Core will generate the appropriate SQL commands to persist these changes to the database.
• Managing database schema: EF Core Migrations allows you to evolve your database schema over time as your application's model changes.

Key Features

• Cross-platform: Works on Windows, macOS, and Linux.
• LINQ support: Allows you to write queries using Language Integrated Query (LINQ).
• Change tracking: EF Core tracks changes to your entities to efficiently generate SQL updates.
• Connection resiliency: Built-in retry logic for transient database errors.
• T4 Templating: Supports custom code generation for models and contexts.
• Extensibility: Designed with extensibility in mind, allowing for custom providers and interceptors.

Getting Started with EF Core

To get started with EF Core, you'll typically need to:

1. Install the necessary EF Core NuGet packages.
2. Define your domain entities (POCO classes).
3. Define a DbContext class that represents a session with the database.
4. Configure your database provider (e.g., SQL Server, SQLite, PostgreSQL).
5. Use the DbContext to query and save data.

Example: Defining a Model

Here's a simple example of defining a Blog entity:

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    public List<Post> Posts { get; set; }
}

public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }

    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}
        

Example: Defining a DbContext

And a corresponding DbContext:

using Microsoft.EntityFrameworkCore;

public class BloggingContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("Server=(localdb)\\mssqllocaldb;Database=Blogging;Trusted_Connection=True;");
    }
}
        

Further Reading

• Modeling your data with EF Core
• Querying data with EF Core
• Saving data with EF Core
• Working with Migrations