Using Entity Framework Core for Data Access

Introduction

Entity Framework Core (EF Core) is a lightweight, extensible, and cross-platform version of the popular Entity Framework data access technology. In this tutorial, we will explore how to use EF Core for data access in a .NET application, from setup to querying and saving data.

Setting Up EF Core

To get started, we need to set up EF Core in our .NET project.

// Open your .NET project in Visual Studio
// Install the following NuGet packages:
// - Microsoft.EntityFrameworkCore
// - Microsoft.EntityFrameworkCore.SqlServer (or another database provider)
// - Microsoft.EntityFrameworkCore.Tools

// Use the NuGet Package Manager Console or the command line:
// Install-Package Microsoft.EntityFrameworkCore
// Install-Package Microsoft.EntityFrameworkCore.SqlServer
// Install-Package Microsoft.EntityFrameworkCore.Tools

Creating the Data Model

Define your data model by creating entity classes that represent the tables in your database.

using System.ComponentModel.DataAnnotations;

public class Product
{
    [Key]
    public int Id { get; set; }

    [Required]
    public string Name { get; set; }

    public decimal Price { get; set; }
}

Creating the DbContext

Create a DbContext class that represents a session with the database and provides an API for performing CRUD operations.

using Microsoft.EntityFrameworkCore;

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

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

Migrations

Use migrations to create and update the database schema based on your data model.

// Open the NuGet Package Manager Console
// Add an initial migration
Add-Migration InitialCreate

// Apply the migration to the database
Update-Database

Querying Data

Use LINQ queries to retrieve data from the database.

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        using (var context = new ApplicationDbContext())
        {
            var products = context.Products.ToList();
            foreach (var product in products)
            {
                Console.WriteLine($"Product: {product.Name}, Price: {product.Price}");
            }
        }
    }
}

Inserting Data

To insert data into the database, add new entities to the DbSet and call SaveChanges.

using System;

class Program
{
    static void Main()
    {
        using (var context = new ApplicationDbContext())
        {
            var newProduct = new Product
            {
                Name = "New Product",
                Price = 9.99m
            };

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

Updating Data

To update data, retrieve the entity, modify its properties, and call SaveChanges.

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        using (var context = new ApplicationDbContext())
        {
            var product = context.Products.First();
            product.Price = 19.99m;

            context.SaveChanges();
        }
    }
}

Deleting Data

To delete data, remove the entity from the DbSet and call SaveChanges.

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        using (var context = new ApplicationDbContext())
        {
            var product = context.Products.First();
            context.Products.Remove(product);

            context.SaveChanges();
        }
    }
}

Conclusion

In this tutorial, you learned how to use Entity Framework Core for data access in a .NET application. We covered setting up EF Core, creating the data model and DbContext, performing migrations, and basic CRUD operations.