Topic 14924 min readStructured Tutorial

Introduction to Entity Framework Core

Quick Answer

Entity Framework Core (EF Core) is a lightweight, extensible, and cross-platform Object-Relational Mapper (ORM) for .NET. It enables C# developers to work with databases using .NET objects, eliminating most of the data-access code they usually need to write.

Learning Objectives

Explain the purpose of Introduction to EF Core in a practical learning context.
Identify the main ideas, terms, and decisions involved in Introduction to EF Core.
Apply Introduction to EF Core in a simple real-world scenario or practice task.

Introduction

Entity Framework Core (EF Core) is a popular Object-Relational Mapper (ORM) for .NET developers. It simplifies database interactions by allowing you to work with data as strongly typed objects.

EF Core supports multiple database providers and works across platforms, making it a versatile choice for modern C# applications.

Work with data using objects, not SQL.

What is Entity Framework Core?

EF Core is an open-source ORM developed by Microsoft. It abstracts database operations into C# code, reducing the need to write raw SQL queries.

It supports common database operations like querying, inserting, updating, and deleting data through LINQ and entity classes.

Cross-platform and lightweight
Supports multiple database providers (SQL Server, SQLite, PostgreSQL, etc.)
Enables Code First and Database First development approaches
Integrates well with ASP.NET Core applications

Key Concepts of EF Core

Understanding EF Core requires familiarity with several core concepts that define how it works.

DbContext: The primary class responsible for interacting with the database.
Entities: Classes that map to database tables.
Migrations: A way to incrementally update the database schema as your model changes.
LINQ Queries: Language Integrated Query used to retrieve data from the database.

DbContext

DbContext represents a session with the database and provides APIs to perform CRUD operations.

Manages entity objects during runtime
Tracks changes to entities
Handles database connections and transactions

Entities and Models

Entities are C# classes that correspond to tables in the database. Each property maps to a column.

Define properties for data fields
Use data annotations or Fluent API for configuration
Support relationships like one-to-many and many-to-many

Setting Up EF Core in a C# Project

To start using EF Core, you need to install the necessary NuGet packages and configure your DbContext.

Install Microsoft.EntityFrameworkCore package
Install a database provider package, e.g., Microsoft.EntityFrameworkCore.SqlServer
Create a DbContext class inheriting from EF Core's DbContext
Configure the connection string in your application

Basic Example: Defining a Model and DbContext

Here is a simple example demonstrating how to define an entity and a DbContext.

Practical Example

This example defines a Product entity and an AppDbContext with a Products DbSet representing the Products table.

Examples

Simple EF Core Model and DbContext

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

public class AppDbContext : DbContext
{
    public DbSet<Product> Products { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("YourConnectionStringHere");
    }
}

This example defines a Product entity and an AppDbContext with a Products DbSet representing the Products table.

Best Practices

Keep your entity classes simple and focused on data.
Use migrations to manage database schema changes.
Leverage LINQ for querying data instead of raw SQL.
Dispose DbContext instances properly to free resources.
Configure relationships explicitly when needed for clarity.

Common Mistakes

Not using migrations and manually changing the database schema.
Keeping DbContext alive too long, causing memory leaks.
Ignoring asynchronous methods for database operations.
Overcomplicating entity models with business logic.

Hands-on Exercise

Create a Simple EF Core Model

Define a C# class representing a 'Customer' with properties Id, Name, and Email, then create a DbContext with a DbSet for customers.

Expected output: A Customer class and a DbContext class with a DbSet<Customer> property.

Hint: Use the example provided as a template and replace the entity with Customer.

Interview Questions

What is DbContext in EF Core?

Interview

DbContext is the primary class in EF Core that manages database connections, tracks changes to entities, and provides APIs to query and save data.

What are migrations in EF Core?

Interview

Migrations are a way to incrementally update the database schema to keep it in sync with the application's data model.

What is Introduction to EF Core, and why is it useful?

Beginner

Entity Framework Core (EF Core) is a lightweight, extensible, and cross-platform Object-Relational Mapper (ORM) for .NET.