In this article I will explain with an example, what is ORM and how to use in ASP.Net Core.
Note: For beginners in ASP.Net Core 7, please refer my article ASP.Net Core 7: Hello World Tutorial with Sample Program example.
 
 

What is ORM?

1. ORM stands for Object-Relational-Mapping, it's used in software development to connect and work with databases using an object-oriented programming language, like C# and Java.
2. An ORM library encapsulates the code needed to manipulate the data, thus removing the use of SQL. One can directly interact with an objects rather than SQL queries, improving code readability and maintainability.
3. It maps database Tables to Classes, Rows and Columns to object properties.
4. Repetitive SQL code is reduced, enabling faster application development.
5. Database independence is achieved, thus facilitating easier migration across different database systems.
6. It centralizes data access logic, reducing the risk of errors and SQL injection attacks.
7. Entity Framework is a full-featured ORM framework.
 
 

Database

Here I am making use of Microsoft’s Northwind Database. You can download it from here.
Download and install Northwind Database
 
 

Model

1. Once the package is successfully installed, create a Folder named Models in your project and then a new class by right clicking the Models folder and then click on Add and then New Item option of the Context Menu.
What is ORM and How to use in ASP.Net Core
 
2. Create the following properties inside the Model class as shown below.
Note: In this article, only four Columns will be displayed and hence four properties are added to the class.
 
public class Customer
{
    public string CustomerID { get; set; }
    public string ContactName { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
}
 
 

Database Context

1. Now you will need to add a new class to your project by right clicking the Solution Explorer and then click on Add and then New Item option of the Context Menu.
What is ORM and How to use in ASP.Net Core
 
2. Inside the class, first inherit the EntityFrameworkCore namespace and then inherit the DbContext class.
Then using Dependency Injection, a Constructor is created DbContextOptions are passed as parameter and also the Constructor of base class i.e. DbContext class is inherited.
Note: For more details on Dependency Injection, please refer my article .Net Core 7: Dependency Injection in ASP.Net Core.
 
Finally, a DbSet Collection property of Customer Model class is created, which will be later used for holding the Data fetched from SQL Server database.
using EF_Core_7_MVC.Models;
using Microsoft.EntityFrameworkCore;
 
namespace EF_Core_7_MVC
{
    public class DBCtx : DbContext
    {
        public DBCtx(DbContextOptions<DBCtx> options) : base(options)
        {
        }
 
        public DbSet<Customer> Customers { get; set; }
    }
}
 
 

Adding the Connection String inside AppSettings.json

The following Connection String setting has been added in the AppSettings.json file.
{
 "ConnectionStrings": {
    "MyConn": "Data Source=.\\SQL2022;Initial Catalog=Northwind;Integrated Security=True"
 }
}
 
 

Configuring Database Context in Program.cs

Inside the Program.cs file, the Connection String is read from the AppSettings.json file and is used to add the DbContext service to the WebApplicationBuilder class.
Note: For more details on reading Connection String inside the Program.cs file, please refer my article .Net Core 7: Read Connection String inside Program.cs from AppSettings.json file.
 
using EF_Core_7_MVC;
using Microsoft.EntityFrameworkCore;
 
var builder = WebApplication.CreateBuilder(args);
 
// Enabling MVC
builder.Services.AddControllersWithViews();
string conStr = builder.Configuration.GetSection("ConnectionStrings")["MyConn"];
builder.Services.AddDbContext<DBCtx>(options => options.UseSqlServer(conStr));
 
var app = builder.Build();
 
//Configuring Routes
app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");
 
app.Run();
 
 

Controller

The Controller consists of following Action method.

Action method for handling GET operation

Inside this Action method, the Top 10 records are fetched from the Customers Table of the Northwind Database using Entity Framework and returned to the View.
public class HomeController : Controller
{
    private DBCtx Context { get; }
    public HomeController(DBCtx _context)
    {
        this.Context = _context;
    }
 
    public IActionResult Index()
    {
        List<Customer> customers = (from customer in this.Context.Customers.Take(10)
                                    select customer).ToList();
        return View(customers);
    }
}
 
 

View

HTML Markup

Inside the View, in the very first line the Customer is declared as IEnumerable which specifies that it will be available as a Collection.
For displaying the records, an HTML Table is used. A FOR EACH loop will be executed over the Model which will generate the HTML Table rows with the Customer records.
@using EF_Core_7_MVC.Models;
@model IEnumerable<Customer>
 
@{
    Layout = null;
}
 
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <h4>Customers</h4>
    <hr />
    <table cellpadding="0" cellspacing="0">
        <tr>
            <th>Customer Id</th>
            <th>ContactName</th>
            <th>City</th>
            <th>Country</th>
        </tr>
        @foreach (Customer customer in Model)
        {
            <tr>
                <td>@customer.CustomerID</td>
                <td>@customer.ContactName</td>
                <td>@customer.City</td>
                <td>@customer.Country</td>
            </tr>
        }
    </table>
</body>
</html>
 
 

Screenshot

What is ORM and How to use in ASP.Net Core
 
 

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