How to seed data in .NET Core 6 with Entity Framework?

Question

I know how to seed data to a database with old .NET 5.0 in startup.cs file using my Seeder class with a Seed() method creating some initial data.

public void Configure(IApplicationBuilder app, IHostingEnvironment env, Seeder seeder)
{
   seeder.Seed();

   ..............
   // other configurations
}

How do I do this in .NET 6.0? There is no place to add my Seeder class as an argument.

Answer 1

I solved a similar problem as follows:

Program.cs (.NET 6)

...
builder.Services.AddScoped<IDbInitializer, DbInitializer>(); //can be placed among other "AddScoped" - above: var app = builder.Build();   

...    
SeedDatabase(); //can be placed above app.UseStaticFiles();
...    
    void SeedDatabase() //can be placed at the very bottom under app.Run()
    {
        using (var scope = app.Services.CreateScope())
        {
            var dbInitializer = scope.ServiceProvider.GetRequiredService<IDbInitializer>();
            dbInitializer.Initialize();
        }
    }

Answer 2

I have never use your solution before. This is what I'm doing,

public class DataContext: DbContext
{
    public DataContext(DbContextOptions options) : base(options)
    {
        
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        new DbInitializer(modelBuilder).Seed();
    }
    
    // Db sets
}

And

public class DbInitializer
{
    private readonly ModelBuilder modelBuilder;

    public DbInitializer(ModelBuilder modelBuilder)
    {
        this.modelBuilder = modelBuilder;
    }

    public void Seed()
    {
        modelBuilder.Entity<User>().HasData(
               new User(){ Id = 1.... },
               new User(){ Id = 2.... },

        );
    }
}

Then run the command

dotnet ef migrations add .......

To create migration file

And

dotnet ef database update

To update db

Answer 3

In my case, I'm using Microsoft.AspNetCore.Identity and needed initialize application with default values in database using seed methods.

builder.Services.AddScoped<UserManager<ApplicationUser>>();
builder.Services.AddScoped<RoleManager<IdentityRole>>();

And after line containing

var app = builder.Build();

I have called the seeds methods:

using (var scope = app.Services.CreateScope())
{
var userManager = scope.ServiceProvider.GetRequiredService<UserManager<Usuario>>();
var roleManager = scope.ServiceProvider.GetRequiredService<RoleManager<IdentityRole>>();
await DefaultRoles.SeedAsync(roleManager);
await DefaultAdmin.SeedAsync(userManager);
}

Answer 4

.NET 6.0

Use these links for detailed version:

• Tutorial: Get started with EF Core in an ASP.NET Core MVC web app
• AspNetCore.Docs

Program.cs

var builder = WebApplication.CreateBuilder(args);

//Add services to the container.
builder.Services.AddDbContext<YourDbContext>(
    optionsBuilder => optionsBuilder.UseSqlServer("Your connection string goes here") //install - Microsoft.EntityFrameworkCore.SqlServer to use ".UseSqlServer" extension method
builder.Services.AddScoped<DbInitializer>();

var app = builder.Build();

//Configure the HTTP-request pipeline
if (app.Environment.IsDevelopment())
{
    app.UseItToSeedSqlServer();    //custom extension method to seed the DB
    //configure other services
}

app.Run();

DbInitializerExtension.cs

internal static class DbInitializerExtension
{
    public static IApplicationBuilder UseItToSeedSqlServer(this IApplicationBuilder app)
    {
        ArgumentNullException.ThrowIfNull(app, nameof(app));

        using var scope = app.ApplicationServices.CreateScope();
        var services = scope.ServiceProvider;
        try
        {
            var context = services.GetRequiredService<YourDbContext>();
            DbInitializer.Initialize(context);
        }
        catch (Exception ex)
        {

        }

        return app;
    }
}

DbInitializer.cs

internal class DbInitializer
{
    internal static void Initialize(YourDbContext dbContext)
    {
        ArgumentNullException.ThrowIfNull(dbContext, nameof(dbContext));
        dbContext.Database.EnsureCreated();
        if (dbContext.Users.Any()) return;

        var users = new User[]
        {
            new User{ Id = 1, Name = "Bruce Wayne" }
            //add other users
        };

        foreach(var user in users)
            dbContext.Users.Add(user);

        dbContext.SaveChanges();
    }
}