Question

I’m a bit confused using Entity Framework 5. I created two interfaces for my entities:

Then I created the classes like the following:

Word:

public class Word : IWord
{
  [Key]
  [Required]
  public int WordId { get; set; }

  [Required]
  public string Tag { get; set; }

  [Required]
  public string Translation { get; set; }

  [Required]
  public char Language { get; set; }

  public string Abbreviation { get; set; }

  //Foreign Key
  public int VocabularyId { get; set; }

  //Navigation
  public virtual IVocabulary Vocabulary { get; set; }
}

Vocabulary:

public class Vocabulary : IVocabulary
{
  [Key]
  [Required]
  public int VocabularyId { get; set; }

  [Required]
  public string Name { get; set; }

  public virtual List<IWord> Words { get; set; }
}

And at the end, in my DataContext I wrote:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
  modelBuilder.Entity<Word>()
    .HasRequired(w => w.Vocabulary)
    .WithMany(v => v.Words)
    .HasForeignKey(w => w.VocabularyId)
    .WillCascadeOnDelete(false);

  base.OnModelCreating(modelBuilder);
}

And I’m getting this error:

Cannot implicitly convert type ‘System.Collections.Generic.List’ to ‘System.Collections.Generic.ICollection’. An explicit conversion exists (are you missing a cast?)

I tried to remove the Interfaces and everything is fine ..

Any helps?

Thanks

Answer 1

Entity framework cannot handle interfaces in navigation properties. It doesn’t know how to materialize them. So you can keep the interfaces on the types (class Word : IWord etc.), but Vocabulary.Words should be an ICollection<Word>.