Simple Entity Framework example in dotnet

Entity Framework (EF) is a popular Object-Relational Mapping (ORM) framework for .NET applications, providing a powerful and intuitive way to interact with databases using C#. Here’s a basic example of how Entity Framework can be used in a .NET application:

Setting Up Entity Framework

1. Install Entity Framework:

   • Entity Framework can be installed via NuGet Package Manager in Visual Studio or using the Package Manager Console:

     Install-Package EntityFramework
     

2. Create a Data Model:

   • Define your data model classes that correspond to database tables. These classes are annotated with attributes that specify mappings to database columns.

   using System.ComponentModel.DataAnnotations;
   
   public class Product
   {
       [Key]
       public int ProductId { get; set; }
   
       [Required]
       public string Name { get; set; }
   
       public decimal Price { get; set; }
   }
   

3. DbContext Class:

   • Create a DbContext class that represents a session with the database and provides APIs to query and save data.

   using System.Data.Entity;
   
   public class AppDbContext : DbContext
   {
       public DbSet<Product> Products { get; set; }
   
       public AppDbContext() : base("name=ConnectionStringName")
       {
       }
   }
   

4. Connection String:

   • Define a connection string in your application configuration file (app.config or web.config) that points to your database.

   <connectionStrings>
       <add name="ConnectionStringName" connectionString="Data Source=YourServer;Initial Catalog=YourDatabase;Integrated Security=True;" providerName="System.Data.SqlClient" />
   </connectionStrings>
   

Using Entity Framework in Application Code

Now, let's see how you can use Entity Framework in your application to perform CRUD operations (Create, Read, Update, Delete).

1. Initialization and Usage:

   • Initialize DbContext instance and perform operations:

   using (var dbContext = new AppDbContext())
   {
       // Create
       var newProduct = new Product { Name = "New Product", Price = 99.99 };
       dbContext.Products.Add(newProduct);
       dbContext.SaveChanges();
   
       // Read
       var product = dbContext.Products.Find(1); // Assuming product with ID 1 exists
       Console.WriteLine($"Product ID: {product.ProductId}, Name: {product.Name}, Price: {product.Price}");
   
       // Update
       product.Price = 109.99;
       dbContext.SaveChanges();
   
       // Delete
       dbContext.Products.Remove(product);
       dbContext.SaveChanges();
   }
   

2. Querying Data:

   • Use LINQ (Language Integrated Query) to query data from the database:

   using (var dbContext = new AppDbContext())
   {
       var expensiveProducts = dbContext.Products.Where(p => p.Price > 100).ToList();
       foreach (var product in expensiveProducts)
       {
           Console.WriteLine($"Product ID: {product.ProductId}, Name: {product.Name}, Price: {product.Price}");
       }
   }