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Getting Started with Entity Framework

This guide will walk you through the essential steps to start using Entity Framework (EF) in your .NET applications. Entity Framework is a powerful Object-Relational Mapper (ORM) that enables developers to work with relational data as if they were using ordinary objects, eliminating much of the data-access code-shredding that developers need to write.

Prerequisites

Before you begin, ensure you have the following installed:

Installation

Entity Framework can be installed via NuGet Package Manager. Open your project in your IDE and install the core EF package:

Using Package Manager Console:

Install-Package Microsoft.EntityFrameworkCore

Using .NET CLI:

dotnet add package Microsoft.EntityFrameworkCore

Depending on your database provider, you'll also need to install a specific EF Core provider package. For example, for SQL Server:

Using Package Manager Console (SQL Server):

Install-Package Microsoft.EntityFrameworkCore.SqlServer

Using .NET CLI (SQL Server):

dotnet add package Microsoft.EntityFrameworkCore.SqlServer

Creating Your First Entity Framework Model

Entity Framework uses models to represent your database schema. You can define your models manually or generate them from an existing database.

1. Define Your Entity Classes

Create plain C# classes that represent your database tables. These are often referred to as Plain Old CLR Objects (POCOs).

Product.cs

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

2. Define Your DbContext Class

The DbContext class is your primary gateway to interacting with your data. It represents a session around a database and allows you to query and save data.

MyDbContext.cs

using Microsoft.EntityFrameworkCore;

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

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        // Replace with your actual connection string
        optionsBuilder.UseSqlServer("Server=(localdb)\\mssqllocaldb;Database=EFDemoDB;Trusted_Connection=True;");
    }
}
Note: The connection string in OnConfiguring is for demonstration purposes. In production, it's recommended to configure the connection string via dependency injection.

Database Migration

Entity Framework Migrations allow you to incrementally update your database schema as your models change. You first need to add the EF Core tools package:

Using Package Manager Console:

Install-Package Microsoft.EntityFrameworkCore.Tools

Using .NET CLI:

dotnet add package Microsoft.EntityFrameworkCore.Tools

Then, create your first migration:

Using Package Manager Console:

Add-Migration InitialCreate

Using .NET CLI:

dotnet ef migrations add InitialCreate

This will generate a C# script that EF uses to create your database. To apply the migration and create the database, run:

Using Package Manager Console:

Update-Database

Using .NET CLI:

dotnet ef database update

Performing Data Operations

Now that your database is set up, you can perform CRUD (Create, Read, Update, Delete) operations.

Adding a New Product

using var context = new MyDbContext();

var newProduct = new Product
{
    Name = "Super Gadget",
    Price = 99.99m,
    ReleaseDate = DateTime.UtcNow
};

context.Products.Add(newProduct);
context.SaveChanges();

Console.WriteLine($"Added product with ID: {newProduct.ProductId}");

Querying Products

using var context = new MyDbContext();

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

var expensiveProducts = context.Products
    .Where(p => p.Price > 50m)
    .OrderBy(p => p.Name)
    .ToList();
Console.WriteLine($"\nExpensive products:");
foreach (var product in expensiveProducts)
{
    Console.WriteLine($"- {product.Name}");
}

Updating a Product

using var context = new MyDbContext();

var productToUpdate = context.Products.Find(1); // Assuming product with ID 1 exists
if (productToUpdate != null)
{
    productToUpdate.Price = 109.99m;
    context.SaveChanges();
    Console.WriteLine($"Updated price for {productToUpdate.Name}");
}

Deleting a Product

using var context = new MyDbContext();

var productToDelete = context.Products.Find(2); // Assuming product with ID 2 exists
if (productToDelete != null)
{
    context.Products.Remove(productToDelete);
    context.SaveChanges();
    Console.WriteLine($"Deleted product: {productToDelete.Name}");
}
Tip: Always ensure your DbContext is properly disposed of, typically by using a using statement or registering it with a dependency injection container.

Next Steps

This guide covers the basics of getting started with Entity Framework. To learn more, explore the following topics: