When I run:
dotnet ef migrations add InitDb -s .\DemoProject.API\ -p .\DemoProject.EntityFramework\
I get this error:
Unable to create a 'DbContext' of type ''. The exception 'The seed entity for entity type 'Character' cannot be added because it has the navigation 'Player' set. To seed relationships, add the entity seed to 'Character' and specify the foreign key values {'PlayerId'}.
Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the involved property values.' was thrown while attempting to create an instance.
As the error says, I need to provide the foreign key Player.Id in Character class, which I did, I don't know what's wrong.
Character.cs:
public class Character
{
public Character()
{
DateCreated = DateOnly.FromDateTime(DateTime.Now);
}
public Guid Id { get; set; }
public string NickName { get; set; } = string.Empty;
public string Classes { get; set; }
public int Level { get; set; }
public DateOnly DateCreated { get; set; }
public Guid PlayerId { get; set; }
public Player Player { get; set; }
}
CharacterMapping:
public class CharacterMapping : IEntityTypeConfiguration<Character>
{
public void Configure(EntityTypeBuilder<Character> builder)
{
builder.Property(x => x.NickName).HasMaxLength(20);
builder.Property(x => x.Classes).HasMaxLength(20);
builder.HasIndex(x => x.NickName).IsUnique();
builder.HasOne(c => c.Player)
.WithMany(p => p.Characters)
.HasForeignKey(c => c.PlayerId);
}
}
Player.cs:
public class Player
{
public Player()
{
DateCreated = DateOnly.FromDateTime(DateTime.Now);
}
public Guid Id { get; set; }
public string Account { get; set; }
public string AccountType { get; set; }
public DateOnly DateCreated { get; set; }
public ICollection<Character> Characters { get; set; }
}
PlayerMapping.cs:
public class PlayerMapping:IEntityTypeConfiguration<Player>
{
public void Configure(EntityTypeBuilder<Player> builder)
{
builder.Property(x => x.Account).HasMaxLength(50);
builder.Property(x => x.AccountType).HasMaxLength(10);
builder.HasIndex(x => x.Account).IsUnique();
}
}
AppDbContext:
public class AppDbContext:DbContext
{
public AppDbContext(DbContextOptions options):base(options)
{
}
public DbSet<Player> Players { get; set; }
public DbSet<Character> Characters { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.ApplyConfiguration(new CharacterMapping());
modelBuilder.ApplyConfiguration(new PlayerMapping());
modelBuilder.Entity<Player>()
.HasData(DataSeed.Players);
modelBuilder.Entity<Character>()
.HasData(DataSeed.Characters);
}
}
DataSeed.cs:
public static class DataSeed
{
public static List<Player> Players { get; } =
[
new Player
{
Id = Guid.NewGuid(),
Account = "[email protected]",
AccountType = "Standard"
},
new Player
{
Id = Guid.NewGuid(),
Account = "[email protected]",
AccountType = "Premium"
},
new Player
{
Id = Guid.NewGuid(),
Account = "[email protected]",
AccountType = "Standard"
}
];
public static Character[] Characters { get; } = [
new Character
{
Id = Guid.NewGuid(),
NickName = "Character1",
Classes = "Warrior",
Level = 10,
PlayerId = Players[0].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character2",
Classes = "Mage",
Level = 8,
PlayerId = Players[0].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character3",
Classes = "Ranger",
Level = 12,
PlayerId = Players[1].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character4",
Classes = "Paladin",
Level = 7,
PlayerId = Players[2].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character5",
Classes = "Druid",
Level = 5,
PlayerId = Players[2].Id
}
];
}
In the DataSeed.cs file I already provided foreign key PlayerId for Character class, but I still get that error. I don't know what to do now.
In the DataSeed.cs file I already provided foreign key PlayerId for Character class, but I still get that error. I don't know what to do now.
Well, according to your scenario, description and based on shared code snippet, the error message indicates a conflict between seeding relationships and setting navigation properties directly. Becuase, EF Core 8 requires explicit specification of foreign keys when seeding relationships. When seeding data that includes relationships, such as between Player and Character, you need to ensure that the foreign key properties (PlayerId in this case) are properly set and that the relationships are established correctly.
In your DataSeed class, your Guid.NewGuid() actually result in the error. Using Guid.NewGuid() each time would indeed generate new Id values, causing inconsistency and potential issues in seeding and maintaining relationships. It's important to use fixed values for Ids during seeding to ensure consistency across migrations .
So, in order to fix the issue, set PlayerId after Players are seeded. Therefore, you should modify your seeder as following:
public static class DataSeed
{
public static List<Player> Players { get; } = new List<Player>();
public static Character[] Characters { get; } = new Character[0];
static DataSeed()
{
SeedPlayers();
SeedCharacters();
}
private static void SeedPlayers()
{
Players.AddRange(new[]
{
new Player
{
Id = new Guid("54f2f515-54a1-454a-9585-54a1454a9585"),
Account = "[email protected]",
AccountType = "Standard"
},
new Player
{
Id = new Guid("dc3a0147-b894-48dd-80f4-420c4611a4c9"),
Account = "[email protected]",
AccountType = "Premium"
},
new Player
{
Id = new Guid("366e355c-5153-4e9b-950d-73586836f913"),
Account = "[email protected]",
AccountType = "Standard"
}
});
}
private static void SeedCharacters()
{
Characters = new[]
{
new Character
{
Id = Guid.NewGuid(),
NickName = "Character1",
Classes = "Warrior",
Level = 10,
PlayerId = Players[0].Id // Do like this
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character2",
Classes = "Mage",
Level = 8,
PlayerId = Players[0].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character3",
Classes = "Ranger",
Level = 12,
PlayerId = Players[1].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character4",
Classes = "Paladin",
Level = 7,
PlayerId = Players[2].Id
},
new Character
{
Id = Guid.NewGuid(),
NickName = "Character5",
Classes = "Druid",
Level = 5,
PlayerId = Players[2].Id
}
};
}
}
Note: Make sure the Id you are seeding/mapping has correct matching with the foreign key table.
On Model Creation:
You should modify your model create configuration as following:
modelBuilder.Entity<Player>()
.HasData(DataSeed.Players);
modelBuilder.Entity<Character>()
.HasData(DataSeed.Characters)
.HasOne(c => c.Player)
.WithMany(p => p.Characters)
.HasForeignKey(c => c.PlayerId);
Note: In addition, based on @Gert Arnold comment, I agree, in first times it would work without any problem, But later on it would create the New GUID again and then it would encounter this issue. So you should fixed the Ids with fixed value instead of new GUID each time. So, its better not to use Guid.NewGuid() while seeding data. I would highly recommend you to check this official document for better insight.