MSDN Documentation

Entity Framework

Entity Framework (EF) is a modern object-relational mapper (ORM) for .NET that enables developers to work with relational data using domain-specific objects that conceptually map to relational database schemas. EF Core is the latest version of Entity Framework and is a cross-platform, extensible, and high-performance data access technology for .NET.

What is Entity Framework?

Entity Framework allows you to query a subset of data from a database and issue commands to update the data store, all within object-oriented paradigms. EF provides a layered abstraction over the ADO.NET data providers, allowing you to interact with your database using .NET objects instead of writing raw SQL queries.

Key Features

• Object-Relational Mapping (ORM): Maps database tables to C# classes and rows to objects.
• LINQ to Entities: Allows you to query your database using Language Integrated Query (LINQ).
• Change Tracking: Automatically tracks changes made to retrieved entities.
• Migrations: Manages database schema changes over time.
• Model First, Database First, Code First: Supports different approaches to defining your data model.
• Performance Optimizations: Designed for high performance and efficiency.

Getting Started with EF Core

To start using EF Core, you'll typically:

1. Install the EF Core NuGet Packages: Add the necessary packages to your project (e.g., Microsoft.EntityFrameworkCore, Microsoft.EntityFrameworkCore.SqlServer).
2. Define Your Model: Create C# classes to represent your database entities.
3. Create a DbContext: A class that inherits from DbContext and represents a session with the database.
4. Configure the Database Connection: Specify the connection string to your database.
5. Use LINQ to Query Data: Write LINQ queries against your DbSet properties in the DbContext.
6. Save Changes: Use the DbContext.SaveChanges() method to persist changes to the database.

Example: Code First Approach

Here's a simple example using the Code First approach:

Entity Class:

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

DbContext:

using Microsoft.EntityFrameworkCore;

public class ApplicationDbContext : DbContext
{
    public DbSet Products { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        // Replace with your actual connection string
        optionsBuilder.UseSqlServer("Server=(localdb)\\mssqllocaldb;Database=MyDatabase;Trusted_Connection=True;");
    }
}
                

Usage:

using (var context = new ApplicationDbContext())
{
    // Add a new product
    var newProduct = new Product { Name = "Laptop", Price = 1200.50m };
    context.Products.Add(newProduct);
    context.SaveChanges();

    // Query products
    var allProducts = context.Products.ToList();
    foreach (var product in allProducts)
    {
        Console.WriteLine($"- {product.Name}: ${product.Price}");
    }
}
                

Resources

• Entity Framework Core Documentation
• EF Core GitHub Repository
• EF Core NuGet Packages