Do you know to use code migrations?

Most enterprise applications require a database to store data. Once you have a database you need a way to manage the schema.

Entity Framework Code First Migrations allow you to update a database schema rather than recreate it from scratch. This is useful when you have a production database that you want to keep, but you want to make changes to the schema.

Database Schema Management Options

Managing database schemas effectively is crucial for the smooth operation and evolution of software applications. For more options to manage database schemas, see the best tools for updating database schemas.

Configuring Entity Framework Code First Migrations

The following assumes you have an existing project with a database context, entities, and have already installed the EF Core nuget packages.

1. Install EF Core Tools

   dotnet new tool-manifest
   dotnet tool install dotnet-ef

2. Enable migrations

   dotnet ef migrations add InitialCreate

   This will create a migration file in your project. This file contains the code to create the database schema.

   // Example of EF Core Migration in a .NET 8 project
   public partial class AddUserTable : Migration
   {
       protected override void Up(MigrationBuilder migrationBuilder)
       {
           migrationBuilder.CreateTable(
               name: "Users",
               columns: table => new
               {
                   Id = table.Column<int>(nullable: false)
                       .Annotation("SqlServer:Identity", "1, 1"),
                   Name = table.Column<string>(nullable: true)
               },
               constraints: table =>
               {
                   table.PrimaryKey("PK_Users", x => x.Id);
               });
       }
   
       protected override void Down(MigrationBuilder migrationBuilder)
       {
           migrationBuilder.DropTable(
               name: "Users");
       }
   }

3. Update database

   dotnet ef database update

Using Rider

If you struggle to remember the commands above, Rider has a great UI that makes creating migrations easy. This is especially useful when you have different projects for both startup and migrations.

Executing Entity Framework Code First Migrations

Once you have some migration, you'll then need to decide when these get run. Naively, developers will often run migrations during program start-up, but this is not recommended. Doing so can cause issues in a web farm environment, as well as cause unnecessary delays during start-up.

var dbContext = scope.ServiceProvider.GetRequiredService<EagleEyeDbContext>();
await dbContext.Database.MigrateAsync();

Entity Framework Migration Bundles

A place to run migrations is during your CICD deployment pipeline.

dotnet ef migrations bundle --self-contained --force
.\efbundle.exe --connection {$ENVVARWITHCONNECTION}