Code-First Approach in Entity Framework Core

Last Updated: August 14, 2020

In Code-First approach you create the entity classes only. Then with migration commands the EF Core creates the database based on these entity classes.

This tutorial is a part of Entity Framework Core series.

This approach is helpful in situations where you are starting with the development of a new project and don’t have a clear picture of the database. To understand how the Code-First approach works, first create a new ASP.NET Core project and Install Entity Framework Core on it.

If you had worked with previous Entity Framework 6 then you would have used the Database-First approach and created EDMX file. The EDMX file contains snapshot of the database, it’s table, stored procedures, relationships, etc. Now the shift is mode to Code-First approach, in-fact Microsoft has placed heavy emphasis on the Code-First approach. You can say Database-First approach is all but dead.

ASP.NET Core Project

In this project I will be dealing with a Company informations like it’s employees, departments, etc.

Create Entity & Context classes

Create a class Information.cs inside the Models folder. It will contain information about the company like company id, name, license, year of establishment and yearly revenue.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace CodeFirst.Models
{
    public class Information
    {
        public int Id { get; set; }

        public string Name { get; set; }

        public string License { get; set; }

        public DateTime Establshied { get; set; }

        public decimal Revenue { get; set; }
    }
}

Next create a Database Context Class (DbContext) and name it CompanyContext.cs. Place it inside the Models folder.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace CodeFirst.Models
{
    public class CompanyContext : DbContext
    {
        public DbSet<Information> Information { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                optionsBuilder.UseSqlServer(@"Server=vaio;Database=Company;Trusted_Connection=True;");
            }
        }
    }
}

Performing Migrations

With Migrations you can create the database based on the Entity & Database Context classes. Check that inside the OnConfiguring() method I have provided the connection string for the database. Here in this case the database name is company.

In Visual Studio, open NuGet Package Manager Console from Tools ➤ NuGet Package Manager ➤ Package Manager Console and enter the following command to create a migration.

PM> add-migration CompanyDB

Or, you can do the same thing with dotnet CLI by executing the following command:

PM> dotnet ef migrations add CompanyDB

The command will create a Migrations folder on your project.

I have written complete tutorial on EF Core Migrations. You will find it very useful.

Now create the database by executing the update-database migration command on the Package Manager Console:

PM> update-database –verbose

Or, you can run the dotnet CLI command to do the same thing:

PM> dotnet ef database update

The command will execute and will create the Company database which you can open and see on your SQL Server.

Inserting a Record on the Table using EF Core

Now that my database is ready, let me insert a record on the Information table.

Add the following code on a Index Action of your Controller.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using CodeFirst.Models;
using Microsoft.AspNetCore.Mvc;

namespace CodeFirst.Controllers
{
    public class HomeController : Controller
    {
        public string Index()
        {
            using (var context = new CompanyContext())
            {
                var info = new Information()
                {
                    Name = "YogiHosting",
                    License = "XXYY",
                    Revenue = 1000,
                    Establshied = Convert.ToDateTime("2014/06/24")
                };
                context.Information.Add(info);
                context.SaveChanges();
            }

            return "Record Inserted";
        }
    }
}

Once the Action is called, the code will execute, and a new record is added to the Information table.

You can see the new record on the SQL Server.