C#•2y ago

❔ Can't seed one-to-many relation efcore

Hello, I am stuck on a error while trying to seed a database with Efcore. DataContext.cs

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        
        var newUser = new User
        {
            Id = "1",
            UserName = "JohnDoe",
            Email = "[email protected]"
        };

        modelBuilder.Entity<User>().HasData(newUser);

        var newPost = new Post
        {
            Id = "1",
            Content = "Hello World!",
            CreatedAt = DateTime.Now,
            UpdatedAt = DateTime.Now,
            UserId = newUser.Id,
            User = newUser
        };
        
        modelBuilder.Entity<Post>().HasData(newPost);
    }

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        
        var newUser = new User
        {
            Id = "1",
            UserName = "JohnDoe",
            Email = "[email protected]"
        };

        modelBuilder.Entity<User>().HasData(newUser);

        var newPost = new Post
        {
            Id = "1",
            Content = "Hello World!",
            CreatedAt = DateTime.Now,
            UpdatedAt = DateTime.Now,
            UserId = newUser.Id,
            User = newUser
        };
        
        modelBuilder.Entity<Post>().HasData(newPost);
    }

User.cs

public class  User : IdentityUser
{
    public Uri? ProfilePicture { get; set; }
    public List<Post> Posts { get; set; } = new();
}

public class  User : IdentityUser
{
    public Uri? ProfilePicture { get; set; }
    public List<Post> Posts { get; set; } = new();
}

Post.cs

using System.ComponentModel.DataAnnotations;

namespace Tweeter.Shared.Models;

public class Post
{
    public String Id { get; set; }
    [Required, MaxLength(280)]
    public string Content { get; set; } = "";
    public DateTime CreatedAt { get; set; }
    public DateTime UpdatedAt { get; set; }
    public string UserId { get; set; } = "";
    public User User { get; set; } = new();
}

using System.ComponentModel.DataAnnotations;

namespace Tweeter.Shared.Models;

public class Post
{
    public String Id { get; set; }
    [Required, MaxLength(280)]
    public string Content { get; set; } = "";
    public DateTime CreatedAt { get; set; }
    public DateTime UpdatedAt { get; set; }
    public string UserId { get; set; } = "";
    public User User { get; set; } = new();
}

I have tried to put the Post inside of .OwnsMany, but that didn't work. How can I fix this?

18 Replies

Nergy101•2y ago

It's never just "a error", Its always important What error. Could you share it in full?

jonathanmOP•2y ago

Oh yeah sorry, forgot to share: The seed entity for entity type 'Post' cannot be added because it has the navigation 'User' set. To seed relationships, add the entity seed to 'Post' and specify the foreign key values {'UserId'}. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the involved property values.

Patrick•2y ago

if you're trying to use skip navigations you cannot configure it as such. if you want to use FKs like that, you need to declare a join table.

Patrick•2y ago

https://learn.microsoft.com/en-us/ef/core/modeling/relationships/many-to-many it's all explained here.

Many-to-many relationships - EF Core

How to configure many-to-many relationships between entity types when using Entity Framework Core

jonathanmOP•2y ago

But this is a One-to-many relation. I don't understand whats wrong with it.

Patrick•2y ago

= new() you also really shouldn't do this on your nav props.

Nergy101•2y ago

Have you tried just using the User HasData() And nesting a single user with it's post, leaving all ID-fields null? Curious if that would work

Patrick•2y ago

apologies i misread as many:many - you should not be newing up user it'll be setting the user id to 0 and thus be inserting a new user well, in the case of string, won't at all your nav props are set by EF or not at all.

jonathanmOP•2y ago

Okay, thank you Is this good?

cs public List<Post> Posts { get; set; } = new List<Post>();

cs public List<Post> Posts { get; set; } = new List<Post>();

Do you mean this?

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        
        var newUser = new User
        {
            UserName = "JohnDoe",
            Email = "[email protected]"
        };

        modelBuilder.Entity<User>(u =>
        {
            u.HasData(newUser);
            u.OwnsOne(s => s.Posts).HasData(new Post
            {
                Content = "Hello World!",
                CreatedAt = DateTime.Now,
                UpdatedAt = DateTime.Now,
                UserId = newUser.Id,
            });
        });
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        
        var newUser = new User
        {
            UserName = "JohnDoe",
            Email = "[email protected]"
        };

        modelBuilder.Entity<User>(u =>
        {
            u.HasData(newUser);
            u.OwnsOne(s => s.Posts).HasData(new Post
            {
                Content = "Hello World!",
                CreatedAt = DateTime.Now,
                UpdatedAt = DateTime.Now,
                UserId = newUser.Id,
            });
        });
}

Patrick•2y ago

that's fine

jonathanmOP•2y ago

because I get the error The seed entity for entity type 'List<Post>' cannot be added because no value was provided for the required property 'Capacity'.

Patrick•2y ago

i wouldn't seed data that way 😄 it needs an array, anyway

Nergy101•2y ago

Well, that explains itself now doesn't it? =) That's a whole other discussion I think, Focusing on getting his code to work with minimal changes atm hehe

Patrick•2y ago

u.OwnsOne(s => s.Posts).HasData(new []
{
  new Post
  {
    Content = "Hello World!",
    CreatedAt = DateTime.Now,
    UpdatedAt = DateTime.Now,
    UserId = newUser.Id,
  }
});

u.OwnsOne(s => s.Posts).HasData(new []
{
  new Post
  {
    Content = "Hello World!",
    CreatedAt = DateTime.Now,
    UpdatedAt = DateTime.Now,
    UserId = newUser.Id,
  }
});

Nergy101•2y ago

Oh sorry, yeah, that's true!

Patrick•2y ago

the user won't have an ID either, so you need to use the nav prop. ... ive been here long enough, thanks 😄

jonathanmOP•2y ago

Thank guys, but I still can't get it working. That is probably because I still don't understand enough about EF. Will try to understand it first.

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Can't seed one-to-many relation efcore