Database not being auto-generated properly Entity Framework + Repos Pattern

Question

I've set up Entity Framework Code First with the Generic Repository Pattern.

Here are my models:

public interface IEntity {
    int Key { get; set; }
}

public class Product : IEntity {
    public int Key {
        get {
            return ID;
        }
        set {
            ID = value;
        }
    }
    public int ID { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
    public IEnumerable<Category> Category { get; set; }

}

public class Category : IEntity {
    public int Key {
        get {
            return ID;
        }
        set {
            ID = value;
        }
    }
    public int ID { get; set; }
    public string Name { get; set; }
    public int ParentID { get; set; }

}

Here is my context that hooks into my generic repo:

public class EntitiesContext : DbContext, IDbContext {

    public DbSet<Product> Products { get; set; }
    public new IDbSet<T> Set<T>() where T : class {
        return base.Set<T>();
    }
}

As you can see Product has a IEnumerable of Category. If I were to create a database to match this is would be like so:

Product - ID - Name - etc.

Category - ID - Name - etc.

ProductCategories - ProductID - CategoryID

How come when my database is created that there is no joining table?

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Community · Accepted Answer · 2017-05-23 11:57:46Z

1

I'm pretty sure it is because you are defining the collection as an IEnumerable<T>. I think that Entity Framework needs at least an ICollection<T> to make the relationship. This SO post covers most of it.

So, change this:

public IEnumerable<Category> Category { get; set; }

To this:

public ICollection<Category> Category { get; set; }

Further, if you want to lazy load the collection, then also make it virtual:

public virtual ICollection<Category> Category { get; set; }

edited May 23, 2017 at 11:57

CommunityBot

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answered Mar 8, 2013 at 9:15

Davin Tryon

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3 Comments

Smithy Over a year ago

You're right, it worked. I also added public ICollection<Product> Products { get; set; } to my Category model to create the correct table and relationships. p.s. thanks for the lazy loading tip too :)

Smithy Over a year ago

actually, in my View Models (these are my DTOs) should i continue to use Icollection stick with Ienumerable or doesn't it matter?

Davin Tryon Over a year ago

I would suggest to use the 'lightest' object possible. You should be able to set an IEnumerable from an ICollection since ICollection inherits from IEnumerable. So, the choice is up to you. ICollection is more efficient if you are indexing into the collection.

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