Question

I am using Entity Framework 4.1 (code first) and have defined entities similar to the following

public class ImageItem
{
    [Column(IsDbGenerated = true, IsPrimaryKey = true, AutoSync = AutoSync.OnInsert)]
    public int Id { get; set; }
    public string ImageUrl { get; set; }
    public int Height { get; set; }
    public int Width { get; set; }
    // other stuff in here
}

public class MyItemWithImages
{
    [Column(IsDbGenerated = true, IsPrimaryKey = true, AutoSync = AutoSync.OnInsert)]
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<ImageItem> Thumbnails { get; set; }
    // other stuff in here
}

What I am trying to achieve is to add another property to hold a “MainImage” item of type ImageItem, that does not necessarily appear in the thumbnails collection.

I have tried adding the following

public virtual ImageItem MainImage { get; set; }

but this overrides the relationship between the MyItemWithImages.Thumbnails collection – not what I would like to happen.

Can anyone point me in the right direction to add this new property, please?

Answer 1

You will need to use the fluent mappings to map your model.

Override the OnModelCreating method of your custom DbContext

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<MyItemWithImages>()
    .HasMany(m => m.Thumbnails)
    .WithOptional()
    .Map(m => m.MapKey("foreignKeyColumnName"));

    modelBuilder.Entity<MyItemWithImages>()
    .HasOptional(m => m.MainImage)
    .WithMany()
    .Map(m => m.MapKey("foreignKeyColumnName"));
}

If you have included the Foreign Key columns as properties then use those in the mappings.

Go through the Fluent Mapping API for more details about mappings.