Question

I’m using ASP.NET MVC 3 with the Entity Framework 4 code first approach and every time I try to specify composite keys using the key attribute on my models, I get this error:

System.Data.Edm.EdmAssociationConstraint: : Number of Properties in
the Dependent and Principal Role in a relationship constraint must be
exactly identical.

I’m using the column attribute to differentiate ordering of the primary keys like so:

 public class Game
    {
        [Key, Column(Order=0)]
        public Guid GameId { get; set; }
        [Key, Column(Order=1)]
        public string Name { get; set; }
        public string Description { get; set; }
        public Game()
        {
            this.GameId = Guid.NewGuid();
        }
    }

I would like to know if there is another approach to creating composite keys, or perhaps there is a way to stop getting this error? I know that it’s possible to add logic to the OnModelBuild event, but I’d rather use the key attributes on the model if possible.

Answer 1

Try to exclude property Name from the entity key (that I would recommend). Or, use it in all entities if you really need to make it part of the key.