ProgrammaticMigrations.cs

await using var context = new BlogContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

using var ctx = new BlogContext();

var services = new ServiceCollection()
    .AddEntityFrameworkDesignTimeServices()
    .AddDbContextDesignTimeServices(ctx);

var npgsqlDesignTimeServices = new NpgsqlDesignTimeServices();
npgsqlDesignTimeServices.ConfigureDesignTimeServices(services);

var serviceProvider = services.BuildServiceProvider();
var scaffolder = serviceProvider.GetRequiredService<IMigrationsScaffolder>();
var migration = scaffolder.ScaffoldMigration(
    "MyMigration",
    "MyApp.Data");
Console.WriteLine(migration.MigrationCode);

public class BlogContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseNpgsql("Host=localhost;Username=test;Password=test")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();
}

public class Blog
{
    public int Id { get; set; }
    public string Name { get; set; }

    public List<Post> Posts { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public string Title { get; set; }
    public Blog Blog { get; set; }
}