What is EF Core?

Entity Framework Core (EF Core) is a modern, lightweight, cross-platform ORM (Object

Relational Mapper) from Microsoft.

It allows .NET developers to work with databases using .NET objects, without writing most

SQL manually.

EF Core handles:

• Mapping classes → database tables
• LINQ → SQL translation
• Tracking changes
• Saving data (SaveChanges())

Example:

var product = new Product { Name = "Laptop", Price = 1200 };

_context.Products.Add(product);

_context.SaveChanges();

This automatically executes an INSERT statement in the database.

⚙ 2. What are the differences between EF Core and EF

Feature EF 6 EF Core

Platform .NET Framework only Cross-platform (.NET 6/7/8)

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Architecture Monolithic Modular, lightweight

LINQ Support Mature, stable Constantly improving

Lazy Loading Built-in Requires setup

Migrations Code-based Improved and more flexible

Database

Providers

Limited (SQL Server,

etc.)

Many (PostgreSQL, MySQL, SQLite, Cosmos

DB, etc.)

Performance Slower Much faster, optimized

EF Core is not just EF 6 ported — it was rewritten from scratch for .NET Core.

🧱 3. How do you configure DbContext in ASP.NET

Core?

DbContext represents a session with the database — it’s where you query and save data.

You register it in the dependency injection container inside Program.cs.

Example:

builder.Services.AddDbContext<AppDbContext>(options =>

options.UseSqlServer(builder.Configuration.GetConnectionString("Defa

ultConnection")));

AppDbContext class:

public class AppDbContext : DbContext

public AppDbContext(DbContextOptions<AppDbContext> options) :

base(options) { }

public DbSet<Product> Products { get; set; }

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🧱 4. What are Migrations?

Migrations allow you to evolve your database schema as your models change, without

losing existing data.

Commands:

dotnet ef migrations add InitialCreate

dotnet ef database update

This creates a Migrations folder with code that applies schema changes automatically.

🧩 5. What is the OnModelCreating method used for?

OnModelCreating is where you configure entity behavior and relationships using the

Fluent API.

Example:

protected override void OnModelCreating(ModelBuilder modelBuilder)

modelBuilder.Entity<Product>()

.Property(p => p.Name)

.HasMaxLength(100)

.IsRequired();

modelBuilder.Entity<Order>()

.HasMany(o => o.Items)

.WithOne(i => i.Order)

.HasForeignKey(i => i.OrderId);

Use it for constraints, relationships, indexes, seeding, and more.

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💤 6. How do you enable Lazy Loading in EF Core?

Lazy loading means related entities are loaded automatically when accessed.

To enable it:

Install the package:

dotnet add package Microsoft.EntityFrameworkCore.Proxies