How to seed data to multiple tables in .NET Core?

Question

On top of this code I want to seed more data into another table called Cities, How can I approach this problem?

I want to seed new data into the new table Cities but I don't know where to place my code exactly, should I create another Seed file ?

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

namespace Persistence
{
    public class Seed
    {
        public static async Task SeedData(DataContext context) 
        {
            if(context.Countries.Any()) return;

            var countries = new List<Country>
                                {
                new Country {
                    Name = "Albania",
                    CountryCode = "AL"
                },
                new Country {
                    Name = "France",
                    CountryCode = "FR"
                },
                new Country {
                    Name = "Germany",
                    CountryCode = "DE"
                }
            };
            
            await context.Countries.AddRangeAsync(countries);
            await context.SaveChangesAsync();
        }
    }
} 

Same properties for Cities:

CityName
CityCode

Answer 1

Why not have seed method per entity? Here's what I mean:

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

namespace Persistence
{
    public class Seed
    {
        public static async Task SeedData(DataContext context) 
        {
            await SeedCountries(context);
            await SeedCities(context);
        }

        private static async Task SeedCountries(DataContext context)
        {
            if(context.Countries.Any()) return;

            var countries = new List<Country>
                                {
                new Country {
                    Name = "Albania",
                    CountryCode = "AL"
                },
                new Country {
                    Name = "France",
                    CountryCode = "FR"
                },
                new Country {
                    Name = "Germany",
                    CountryCode = "DE"
                }
            };
            
            await context.Countries.AddRangeAsync(countries);
            await context.SaveChangesAsync();
        }

        private static async Task SeedCities(DataContext context)
        {
            if(context.Cities.Any()) return;

            var cities = new List<City> {
                new City {
                    Name = "New York",
                    Code = "NYC"
                },
                new City {
                    Name = "Paris",
                    Code = "PAR"
                },
                new City {
                    Name = "Berlin",
                    Code = "BER"
                }
            };
            
            await context.Cities.AddRangeAsync(cities);
            await context.SaveChangesAsync();
        }
    }
} 

Or use a more generic approach like this:

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

public static class DbSetExtensions
{
    public static async Task SeedDataAsync<TEntity>(this DbSet<TEntity> dbSet, Func<IEnumerable<TEntity>> seedDataCreator) where TEntity : class
    {
        if (dbSet.Any())
        {
            return;
        }

        var data = seedDataCreator.Invoke();

        await dbSet.AddRangeAsync(data);
    }
}

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

namespace Persistence
{
    public class Seed
    {
        private async Task SeedDataAsync(DataContext db)
        {
            await db.Countries.SeedDataAsync(() => new[] {
                    new Country {
                        Name = "Albania",
                        CountryCode = "AL"
                    },
                    new Country {
                        Name = "France",
                        CountryCode = "FR"
                    },
                    new Country {
                        Name = "Germany",
                        CountryCode = "DE"
                    }
                });

            await db.Cities.SeedDataAsync(() => new[] {
                    new City {
                        Name = "New York",
                        Code = "NYC"
                    },
                    new City {
                        Name = "Paris",
                        Code = "PAR"
                    },
                    new City {
                        Name = "Berlin",
                        Code = "BER"
                    }
                });

            await db.SaveChangesAsync();
        }
    }
}