Entity Framework Core

Introduction

Entity Framework Core (EF Core) is a modern, open‑source, object‑relational mapper (ORM) for .NET. It enables developers to work with a database using .NET objects, eliminating the need for most data‑access code that developers usually need to write.

Setup & Installation

Install the EF Core packages via dotnet CLI or NuGet:

dotnet add package Microsoft.EntityFrameworkCore
dotnet add package Microsoft.EntityFrameworkCore.SqlServer   // or any provider
dotnet add package Microsoft.EntityFrameworkCore.Tools

Configure your DbContext in Program.cs:

builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("Default")));

Data Modeling

Define entity classes and a DbContext:

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; }
}

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

    public AppDbContext(DbContextOptions<AppDbContext> options)
        : base(options) { }
}

Working with Migrations

Create and apply migrations using the CLI:

dotnet ef migrations add InitialCreate
dotnet ef database update

Inspect the generated migration files to understand the schema changes.

Querying Data

EF Core supports LINQ queries. Example:

using var context = new AppDbContext();

var blogs = await context.Blogs
    .Include(b => b.Posts)
    .Where(b => b.Url.Contains("dotnet"))
    .OrderBy(b => b.BlogId)
    .ToListAsync();

Use AsNoTracking for read‑only queries to improve performance.

Performance Tips

• Prefer AsNoTracking when updates aren’t required.
• Batch updates/inserts with SaveChangesAsync in a single context.
• Use compiled queries for frequently executed statements.
• Avoid eager loading large navigation graphs; use explicit loading when needed.

Further Resources