Entity framework code first does not create many-to-many database table

Question

I have code first model like shown below. Application creates table 'VideoPosts', and does not create 'ImagePosts'. Is there a problem with CoverImage and TileImage navigation properties, or am I missing something? I want to have a table for images just like table for videos.

public class Post
    {

        public int PostID { get; set; }

        [ForeignKey("TileImageID")]
        public Image TileImage { get; set; }
        [Column("TileImageID")]
        public int? TileImageID { get; set; }
        [ForeignKey("TileImageID")]
        public Image CoverImage { get; set; }
        [Column("CoverImageID")]
        public int? CoverImageID { get; set; }

        public virtual ICollection<Image> Gallery { get; set; }
        public virtual ICollection<Video> VideoGallery { get; set; }
    }

    public class Video
    {
        public int VideoID { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }
        [Required]
        public string Url { get; set; }
        public virtual ICollection<Post> Posts { get; set; }
    }

    public class Image
    {
        public int ImageID { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }
        [Required]
        public string Path { get; set; }

        public virtual ICollection<Post> Posts { get; set; }
    }

vpetrovic · Accepted Answer · 2016-03-17 11:39:41Z

1

I managed to create a desired table with custom mapping. TileImage and CoverImage are also in the model, I think there was no other problems with a model.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

            modelBuilder.Entity<Post>()
                .HasMany<Image>(s => s.Gallery)
                .WithMany(c => c.Posts)
                .Map(cs =>
                {
                    cs.MapLeftKey("PostID");
                    cs.MapRightKey("ImageID");
                    cs.ToTable("PostImages");
                });
        }

answered Mar 17, 2016 at 11:39

vpetrovic

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Comments

James Dev · Accepted Answer · 2016-03-17 10:16:29Z

0

One of your foreign key annotations is wrong other than that I don't see anything wrong with your DB.

    [ForeignKey("TileImageID")]
    public Image TileImage { get; set; }
    [Column("TileImageID")]
    public int? TileImageID { get; set; }
    [ForeignKey("CoverImageID")]
    public Image CoverImage { get; set; }
    [Column("CoverImageID")]
    public int? CoverImageID { get; set; }

answered Mar 17, 2016 at 10:16

James Dev

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3 Comments

vpetrovic Over a year ago

I corrected annotation now. Why dont I get a new table called 'ImagePosts', just like 'VideoPosts' (see picture). I want to create many-to-many relationship with Post and Image. One post has many images (Gallery), and one Image can be used in many Posts.

James Dev Over a year ago

Is your database up to date i.e. on the latest migration ?

vpetrovic Over a year ago

Yes, it is up to date, but currently I am not using migrations, I delete database (physically) and detach it, so the database is created from scratch every time I run the app.

GalaxMan · Accepted Answer · 2016-03-17 10:46:13Z

0

Try in DataContext put this:

    public DataContext() : base("DatabaseName")
    {
       // Database.SetInitializer<DataContext>(new DropCreateDatabaseAlways<DataContext>());
        Database.SetInitializer<DataContext>(new CreateDatabaseIfNotExists<DataContext>());
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
    }

Delete physically database and try run application, then application will be automatic create database and then you will see 'ImagePosts'. In your code i don't see anything wrong

answered Mar 17, 2016 at 10:46

GalaxMan

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5 Comments

GalaxMan Over a year ago

Remove comment from first row and put on second row

vpetrovic Over a year ago

Now I get those errors: MyApp.Models.IdentityUserLogin: : EntityType 'IdentityUserLogin' has no key defined. Define the key for this EntityType. MyApp.Models.IdentityUserRole: : EntityType 'IdentityUserRole' has no key defined. Define the key for this EntityType. IdentityUserLogins: EntityType: EntitySet 'IdentityUserLogins' is based on type 'IdentityUserLogin' that has no keys defined. IdentityUserRoles: EntityType: EntitySet 'IdentityUserRoles' is based on type 'IdentityUserRole' that has no keys defined.

vpetrovic Over a year ago

base.OnModelCreating(modelBuilder); must be called. But I still do not have table I want. I think the problem is not in database recreation, maybe the class model is somehow wrong because of TileImage and CoverImage navigation properties.

GalaxMan Over a year ago

I will write you in second comment

vpetrovic Over a year ago

After I commented TileImage and CoverImage fields, a new table 'PostImages' was created as desired, so those fields are the cause of the problem. How can I accomplish to have references to Image by those two fields and to have many to many table for image gallery?

GalaxMan · Accepted Answer · 2016-03-17 11:15:51Z

Your code does't show this, but from the errors you are getting I assume that you are overriding OnModelCreating.This is where IdentityDbContext configure the entity framework mappings. This means that if you want to override OnModelCreating you need to either call the base or you must do the mapping yourself.

So either this:

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
         base.OnModelCreating(modelBuilder);
    }

Or you do the mapping:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<IdentityUserLogin>().HasKey<string>(l => l.UserId);
    modelBuilder.Entity<IdentityRole>().HasKey<string>(r => r.Id);
    modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId });
}

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