C#•3y ago

[EF Core 8] Many-to-many relationship with payload

Hi all,
I am trying to create a many-to-many relationship as described in https://learn.microsoft.com/en-us/ef/core/modeling/relationships/many-to-many#many-to-many-and-join-table-with-payload
My models are the following:

public class Post
{
    public int Id { get; set; }
    public List<Tag> Tags { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class Tag
{
    public int Id { get; set; }
    public List<Post> Posts { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class PostTag
{
    public int PostId { get; set; }
    public int TagId { get; set; }
    public string CustomPayload { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public List<Tag> Tags { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class Tag
{
    public int Id { get; set; }
    public List<Post> Posts { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class PostTag
{
    public int PostId { get; set; }
    public int TagId { get; set; }
    public string CustomPayload { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public List<Tag> Tags { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class Tag
{
    public int Id { get; set; }
    public List<Post> Posts { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class PostTag
{
    public int PostId { get; set; }
    public int TagId { get; set; }
    public string CustomPayload { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public List<Tag> Tags { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class Tag
{
    public int Id { get; set; }
    public List<Post> Posts { get; } = new();
    public List<PostTag> PostTags { get; } = new();
}

public class PostTag
{
    public int PostId { get; set; }
    public int TagId { get; set; }
    public string CustomPayload { get; set; }
}

MyDbContext:

public class MyDbContext : DbContext
{
    public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }
    public virtual DbSet<Post> Posts { get; set; }
    public virtual DbSet<Tag> Tags { get; set; }
}

public class MyDbContext : DbContext
{
    public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }
    public virtual DbSet<Post> Posts { get; set; }
    public virtual DbSet<Tag> Tags { get; set; }
}

public class MyDbContext : DbContext
{
    public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }
    public virtual DbSet<Post> Posts { get; set; }
    public virtual DbSet<Tag> Tags { get; set; }
}

public class MyDbContext : DbContext
{
    public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }
    public virtual DbSet<Post> Posts { get; set; }
    public virtual DbSet<Tag> Tags { get; set; }
}

when I try to create the initial migration I get the following error:

Unable to create a 'DbContext' of type ''. The exception 'The entity type 'PostTag' requires a primary key to be defined. If you intended to use a keyless entity type, call 'HasNoKey' in 'OnModelCreating'

Unable to create a 'DbContext' of type ''. The exception 'The entity type 'PostTag' requires a primary key to be defined. If you intended to use a keyless entity type, call 'HasNoKey' in 'OnModelCreating'

Unable to create a 'DbContext' of type ''. The exception 'The entity type 'PostTag' requires a primary key to be defined. If you intended to use a keyless entity type, call 'HasNoKey' in 'OnModelCreating'

Unable to create a 'DbContext' of type ''. The exception 'The entity type 'PostTag' requires a primary key to be defined. If you intended to use a keyless entity type, call 'HasNoKey' in 'OnModelCreating'

When adding a primary key on the

PostTag

PostTag

PostTag

PostTag model:

Unable to create a 'DbContext' of type ''. The exception 'Cannot use table 'PostTag' for entity type 'PostTag' since it is being used for entity type 'PostTag (Dictionary<string, object>)' and potentially other entity types, but there is no linking relationship. Add a foreign key to 'PostTag' on the primary key properties and pointing to the primary key on another entity type mapped to 'PostTag'.

Unable to create a 'DbContext' of type ''. The exception 'Cannot use table 'PostTag' for entity type 'PostTag' since it is being used for entity type 'PostTag (Dictionary<string, object>)' and potentially other entity types, but there is no linking relationship. Add a foreign key to 'PostTag' on the primary key properties and pointing to the primary key on another entity type mapped to 'PostTag'.

Unable to create a 'DbContext' of type ''. The exception 'Cannot use table 'PostTag' for entity type 'PostTag' since it is being used for entity type 'PostTag (Dictionary<string, object>)' and potentially other entity types, but there is no linking relationship. Add a foreign key to 'PostTag' on the primary key properties and pointing to the primary key on another entity type mapped to 'PostTag'.

Unable to create a 'DbContext' of type ''. The exception 'Cannot use table 'PostTag' for entity type 'PostTag' since it is being used for entity type 'PostTag (Dictionary<string, object>)' and potentially other entity types, but there is no linking relationship. Add a foreign key to 'PostTag' on the primary key properties and pointing to the primary key on another entity type mapped to 'PostTag'.

I have a few questions:

1) What am I missing and cannot make this relationship function?
2) Even if somehow the tables are produced from the migration, will the

PostTag

PostTag

PostTag

PostTag table be able to return the

CustomPayload

CustomPayload

CustomPayload

CustomPayload and how?
3) Is this supposed to be the correct way to supply the join table with a

user defined payload

user defined payload

user defined payload

user defined payload ?

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