EF Core: DbContext & Models

Learn how to define entity models and a DbContext to represent your database in C#.

Entity Classes

An entity is a plain C# class that EF Core maps to a database table. By convention, a property named `Id` (or `{ClassName}Id`) becomes the primary key.

public class TaskItem
{
    public int Id { get; set; }
    public string Title { get; set; } = "";
    public bool IsComplete { get; set; }
}

DbContext

A `DbContext` represents a session with the database — it exposes `DbSet<T>` properties for each entity type, giving you a queryable, LINQ-friendly view of each table.

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

    public DbSet<TaskItem> Tasks { get; set; }
}

Registering DbContext

Program.cs

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

Migrations

Migrations let EF Core translate changes in your C# entity classes into the SQL needed to update your actual database schema.

dotnet ef migrations add InitialCreate
dotnet ef database update

FAQs

Do I need to install a separate CLI tool for migrations?

Yes — run `dotnet tool install --global dotnet-ef` once to get the `dotnet ef` command available.

Summary

Entity classes are plain C# classes mapped to database tables.
DbContext exposes DbSet<T> properties for querying each table.
Migrations translate C# model changes into actual database schema updates.

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