Entity Framework

Overview

Entity Framework (EF) is Microsoft’s recommended data access technology for new .NET applications. It provides an object–relational mapper (ORM) that enables .NET developers to work with a database using .NET objects, eliminating the need for most of the data-access code that developers usually need to write.

On this page Getting Started Modeling Data Queries Saving Data Performance Tips API Reference

Getting Started

Install the EF Core package and create a DbContext.

dotnet add package Microsoft.EntityFrameworkCore
dotnet add package Microsoft.EntityFrameworkCore.SqlServer

Example 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 options)
        => options.UseSqlServer("Server=(localdb)\\mssqllocaldb;Database=Blogging;Trusted_Connection=True;");
}

Modeling Data

Define entity classes that map to database tables.

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; }
}

Use data annotations or the Fluent API for configuration.

Queries

EF supports LINQ queries that are translated to SQL.

using var db = new BloggingContext();

var blogs = db.Blogs
    .Where(b => b.Url.Contains("dotnet"))
    .OrderBy(b => b.BlogId)
    .ToList();

Include related data with Include:

var blogsWithPosts = db.Blogs
    .Include(b => b.Posts)
    .ToList();

Saving Data

Changes are tracked automatically. Call SaveChanges to persist.

using var db = new BloggingContext();

var blog = new Blog { Url = "https://devblogs.microsoft.com/dotnet" };
db.Blogs.Add(blog);
db.SaveChanges();

Update and delete operations follow the same pattern.

Performance Tips

  • Use AsNoTracking for read‑only queries.
  • Batch multiple commands with SaveChanges instead of one per entity.
  • Limit results with Take and Skip for paging.
  • Prefer compiled queries for high‑traffic scenarios.

API Reference

Key classes and interfaces:

  • DbContext
  • DbSet<TEntity>
  • ModelBuilder (Fluent API)
  • EntityEntry
  • RelationalDatabaseFacadeExtensions

Visit the full API documentation for detailed members.

Resources