Fluent API map composite pattern object

Question

I am trying to map a composite object using FluentAPI on entity framework 5.0 for the following model:

public class Category
{
    public int CategoryId { get; set; }
    public string CategoryName { get; set; }
    public virtual ICollection<Category> Children { get; set; }
}

So far tried many ways that didn't work well, such as the following:

HasKey(t => t.CateroryId);
HasOptional(c => c.Children)
   .WithMany()
   .HasForeignKey(c => c.CateroryId);

Any idea how I might do that?

Answer 1

If I've understood what you're going for - a Category is able to have many categories as children.

I've done this in the past using a similar foreign key mapping and some additional properties, although there may be a way to do it using independent association.

Adding additional properties to your Category so we can keep track of the parent/child relationship:

public class Page
{
    public int CategoryId { get; set; }
    public string CategoryName { get; set; }
    public int? ParentID { get; set; } // Nullable (Parent is optional).

    // Navigation properties
    public virtual Category Parent { get; set; } // Optional Parent
    public virtual ICollection<Category> Children { get; set; }
}

You should then be able to configure like so (depending on where your mappings are set):

this.HasMany(c => c.Children)        // Many Children
    .WithOptional(c => c.Parent)     // Optional Parent
    .HasForeignKey(x => x.ParentID);