Entity Framework | Data Access

Introduction to Entity Framework

Entity Framework (EF) is an open-source object-relational mapper (ORM) framework for ADO.NET. It allows developers to interact with a database using .NET objects, eliminating the need for most of the data-access code that developers usually need to write. EF supports LINQ queries, change tracking, and schema migrations.

Setting Up Entity Framework

Before you start using Entity Framework, you need to set it up in your project. This involves installing the necessary packages and configuring your database connection.

Install Entity Framework Core using NuGet Package Manager:

Install-Package Microsoft.EntityFrameworkCore

Alternatively, you can use the .NET CLI:

dotnet add package Microsoft.EntityFrameworkCore

Creating a Model

An EF model includes entity classes and a context class that represents a session with the database, allowing you to query and save data.

Here's an example of a simple model:

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

Setting Up the DbContext

The DbContext class is the main class that coordinates Entity Framework functionality for a given data model. Create a class that inherits from DbContext and configure it to use your model.

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

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

Creating and Applying Migrations

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

Create an initial migration:

Add-Migration InitialCreate

Apply the migration to the database:

Update-Database

Querying Data

Once your model is set up and your database is created, you can start querying data using LINQ queries.

using (var context = new AppDbContext())
{
    var products = context.Products.ToList();
    foreach (var product in products)
    {
        Console.WriteLine($"Product: {product.Name}, Price: {product.Price}");
    }
}

Inserting Data

You can add new records to the database by creating instances of your entity classes and adding them to the relevant DbSet.

using (var context = new AppDbContext())
{
    var product = new Product { Name = "New Product", Price = 9.99m };
    context.Products.Add(product);
    context.SaveChanges();
}

Updating Data

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

using (var context = new AppDbContext())
{
    var product = context.Products.First();
    product.Price = 19.99m;
    context.SaveChanges();
}

Deleting Data

To delete a record, retrieve it and pass it to the Remove method of the DbSet.

using (var context = new AppDbContext())
{
    var product = context.Products.First();
    context.Products.Remove(product);
    context.SaveChanges();
}

Conclusion

Entity Framework is a powerful tool for data access in .NET applications. By following this tutorial, you should now have a basic understanding of how to set up and use EF for common data operations such as querying, inserting, updating, and deleting data.

Entity Framework Tutorial