C#•2y ago

✅ EF Core Relations don't seem to work properly

I'm trying to model a fairly complex set of relations in EntityFramework core / ASP.NET, but am failing to create a new entry as the system insists it already exists; yet the corresponding table in the DB is empty

27 Replies

UpOP•2y ago

[Table("mods")]
public class Mod : BaseModel
{
    public string Slug { get; set; } = null!;
    public IEnumerable<SupportedPlatform> PlatformIDs { get; set; } = null!;
    //...
}

[Table("mods")]
public class Mod : BaseModel
{
    public string Slug { get; set; } = null!;
    public IEnumerable<SupportedPlatform> PlatformIDs { get; set; } = null!;
    //...
}

[Table("mods_supported_platforms")]
public class SupportedPlatform : BaseModel
{
    [Required]
    public Platform Platform { get; set; } = null!;
    
    [Required]
    public string Name { get; set; } = null!;
    
    public Guid PlatformId { get; set; }
}

[Table("mods_supported_platforms")]
public class SupportedPlatform : BaseModel
{
    [Required]
    public Platform Platform { get; set; } = null!;
    
    [Required]
    public string Name { get; set; } = null!;
    
    public Guid PlatformId { get; set; }
}

[Table("platforms")]
public class Platform : BaseModel
{
    [Required]
    public string Slug { get; set; } = null!;
    
    [Required]
    public string Name { get; set; } = null!;
}

[Table("platforms")]
public class Platform : BaseModel
{
    [Required]
    public string Slug { get; set; } = null!;
    
    [Required]
    public string Name { get; set; } = null!;
}

relevant part of my dbcontext init:

modelBuilder.Entity<Mod>().HasIndex(it => it.Slug).IsUnique();
modelBuilder.Entity<Mod>().HasMany(it => it.PlatformIDs);
modelBuilder.Entity<SupportedPlatform>().HasOne(it => it.Platform).WithMany().HasForeignKey(it => it.PlatformId);
modelBuilder.Entity<SupportedPlatform>().HasKey(it => new {it.PlatformId, it.Name});

modelBuilder.Entity<Mod>().HasIndex(it => it.Slug).IsUnique();
modelBuilder.Entity<Mod>().HasMany(it => it.PlatformIDs);
modelBuilder.Entity<SupportedPlatform>().HasOne(it => it.Platform).WithMany().HasForeignKey(it => it.PlatformId);
modelBuilder.Entity<SupportedPlatform>().HasKey(it => new {it.PlatformId, it.Name});

and finally how I'm trying to create a new entry:

public async Task<Mod> AddMod(AddModsInput mod)
    {
        var platformsStore = _dbContext.Platforms.ToList();
        var platforms = mod.SupportedPlatforms.Select(it => new SupportedPlatform()
        {
            Platform = platformsStore.FirstOrDefault(pl => pl.Slug == it.Platform) ?? throw new KeyNotFoundException(),
            Name = it.Id,
        });
        
        var result = new Mod
        {
            Slug = mod.Slug,
            PlatformIDs = platforms,
        };
        
        _dbContext.Mods.Update(result);
        await _dbContext.SaveChangesAsync();
        return result;
    }

public async Task<Mod> AddMod(AddModsInput mod)
    {
        var platformsStore = _dbContext.Platforms.ToList();
        var platforms = mod.SupportedPlatforms.Select(it => new SupportedPlatform()
        {
            Platform = platformsStore.FirstOrDefault(pl => pl.Slug == it.Platform) ?? throw new KeyNotFoundException(),
            Name = it.Id,
        });
        
        var result = new Mod
        {
            Slug = mod.Slug,
            PlatformIDs = platforms,
        };
        
        _dbContext.Mods.Update(result);
        await _dbContext.SaveChangesAsync();
        return result;
    }

error message is

Action Exception | Type: 'InvalidOperationException', Message: 'The instance of entity type 'SupportedPlatform' cannot be tracked because another instance with the key value '{PlatformId: <correct GUID>
ab, Name: <correct name>}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.'

Action Exception | Type: 'InvalidOperationException', Message: 'The instance of entity type 'SupportedPlatform' cannot be tracked because another instance with the key value '{PlatformId: <correct GUID>
ab, Name: <correct name>}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.'

undisputed world champions•2y ago

are you trying to update or insert? _dbContext.Mods.Update(result); is sugesting you trying to update. you should use a Mod that you read from the _dbContext first to update, instead of newing up a new instance

UpOP•2y ago

upsert. if the entity exists -> update it, if not -> create update() works just fine for that by detecting whether the primary key exists or not

undisputed world champions•2y ago

tbh i havent used it like that before but the error message complains about SupportedPlatform which you new up too have you tried useing the ones you read from db? maybe it doesnt work that well for naviagation properties? catshrug

UpOP•2y ago

there are none in the DB I am trying to insert them in this query

undisputed world champions•2y ago

and i guess the platforms are unique too? so platforms doesn't just contain duplicates?

UpOP•2y ago

platforms are unique and only contains the correct keys, yes. SupportedPlatform is essentially an IDictionary<Platform, string> property on Mod ..which means serializing it into a separate table

jcotton42•2y ago

Why are you using IEnumerable?

jcotton42•2y ago

https://learn.microsoft.com/en-us/ef/core/modeling/relationships/conventions also prefer conventions to explicit configuration

Conventions for relationship discovery - EF Core

How navigations, foreign keys, and other aspects of relationships are discovered by EF Core model building conventions

UpOP•2y ago

what else would I use?

jcotton42•2y ago

List<T> IEnumerable is not appropriate for representing a database relationship

UpOP•2y ago

well it never complained about it 😅

jcotton42•2y ago

How are you supposed to add or remove from it?

UpOP•2y ago

I haven't gotten around to that yet, haha

jcotton42•2y ago

Well you'll quickly discover you can't do that with IEnumerable 😛

UpOP•2y ago

ik but more like, I haven't needed to add/remove yet so how do I use conventions to add constraints? because that is what I've mainly been using the fluent api for

jcotton42•2y ago

You explicitly configure what conventions don't suffice

UpOP•2y ago

okay, I've redone the DB and am now able to insert data properly. however, I am unable to retrieve the supported platforms it seems

UpOP•2y ago

UpOP•2y ago

[Table("mods")]
public class Mod : BaseModel
{
    public string Slug { get; set; } = null!;
    
    public ModMetadata Meta { get; set; } = null!;
    
    public ICollection<ModSupportedPlatform> PlatformIDs { get; set; } = new List<ModSupportedPlatform>();
    public ICollection<McVersion> SupportedVersions { get; set; } = new List<McVersion>();

    [GraphField("supportedPlatforms")]
    public IEnumerable<Platform> GetSupportedPlatforms()
    {
        return PlatformIDs.Select(it => it.Platform).AsEnumerable();
    }
}

[Table("mods")]
public class Mod : BaseModel
{
    public string Slug { get; set; } = null!;
    
    public ModMetadata Meta { get; set; } = null!;
    
    public ICollection<ModSupportedPlatform> PlatformIDs { get; set; } = new List<ModSupportedPlatform>();
    public ICollection<McVersion> SupportedVersions { get; set; } = new List<McVersion>();

    [GraphField("supportedPlatforms")]
    public IEnumerable<Platform> GetSupportedPlatforms()
    {
        return PlatformIDs.Select(it => it.Platform).AsEnumerable();
    }
}

UpOP•2y ago

but the data does exist in the DB

UpOP•2y ago

so looks like the navigation properties aren't being populated thonk

UpOP•2y ago

here's how I assign those relations:

        modelBuilder.Entity<Mod>().HasIndex(it => it.Slug).IsUnique();
        modelBuilder.Entity<Mod>().HasOne(it => it.Meta).WithOne(it => it.Mod).HasForeignKey<ModMetadata>(it => it.ModId);
        modelBuilder.Entity<Mod>().HasMany(it => it.PlatformIDs).WithOne(it => it.Mod).HasForeignKey(it => it.ModId);
        modelBuilder.Entity<ModSupportedPlatform>().HasOne(it => it.Platform).WithMany().HasForeignKey(it => it.PlatformId).IsRequired();
        modelBuilder.Entity<ModSupportedPlatform>().HasKey(it => new {it.PlatformId, it.PlatformKey});

        modelBuilder.Entity<Mod>().HasIndex(it => it.Slug).IsUnique();
        modelBuilder.Entity<Mod>().HasOne(it => it.Meta).WithOne(it => it.Mod).HasForeignKey<ModMetadata>(it => it.ModId);
        modelBuilder.Entity<Mod>().HasMany(it => it.PlatformIDs).WithOne(it => it.Mod).HasForeignKey(it => it.ModId);
        modelBuilder.Entity<ModSupportedPlatform>().HasOne(it => it.Platform).WithMany().HasForeignKey(it => it.PlatformId).IsRequired();
        modelBuilder.Entity<ModSupportedPlatform>().HasKey(it => new {it.PlatformId, it.PlatformKey});

jcotton42•2y ago

Try letting EF infer by convention Don't use configuration unless you need to Also, you made and applied a migration right?

UpOP•2y ago

yes update: tried it with implicit properties and even deleted + re-seeded the DB. no change

UpOP•2y ago

also fwiw, when I send the above GQL query, this is the only database query that is executed:

UpOP•2y ago

any other ideas @jcotton42? update: solution was to enable lazy loading proxies via Microsoft.EntityFrameworkCore.Proxies, and mark all my navigation properties as virtual.

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✅ EF Core Relations don't seem to work properly

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