Two FKs in Entity Framework Fluent API

Question

I'm struggling connecting two really simple tables:

[Table("Item")]
public class Item
{
    [Key]
    [Column("itemId", TypeName = "int")]
    public int ItemId { get; set; }
}

[Table("LinkedItems")]
public class LinkedItem
{
    [Key]
    [Column("itemId", TypeName = "int")]
    public int ItemId { get; set; }

    [Column("parentItemId", TypeName = "int")]
    public int ParentItemId { get; set; }
}

There are two Foreign Keys in LinkedItem table:

1. itemId , points to the table Item to show itself

2. parentItemId , points to the table Item to show its parent

I would like to accomplish something like this:

[Table("Item")]
public class Item
{
    [Key]
    [Column("itemId", TypeName = "int")]
    public int ItemId { get; set; }

    public ICollection<LinkedItem> ChildItems { get; set; }
    public LinkedItem LinkedItem { get; set; }
}

[Table("LinkedItems")]
public class LinkedItem
{
    [Key]
    [Column("itemId", TypeName = "int")]
    public int ItemId { get; set; }

    [Column("parentItemId", TypeName = "int")]
    public int ParentItemId { get; set; }

    public Item Item { get; set; }
    public Item ParentItem { get; set; }
}

I was successful with creating connection from Item to LinkedItem:

modelBuilder.Entity<Item>().HasOptional(i => i.LinkedItem).WithRequired(i => i.Item);

but I can't add another connection. Can you help me with Fluent API configuration for these two tables?

Answer 1

A LinkedItem class isn't necessary for this. You can simply accomplish this with one class.

public class Item
{
    public int Id { get; set; }

    public int ParentItemId { get; set; }

    public virtual Item ParentItem { get; set; }

    public virtual ICollection<Item> ChildItems { get; set; }
}

        modelBuilder.Entity<Item>()
            .HasRequired(entity => entity.ParentItem)
            .WithMany(entity => entity.ChildItems)
            .HasForeignKey(entity => entity.ParentItemId);

Otherwise simply add:

modelBuilder.Entity<Item>()
    .HasMany(entity => entity.ChildItems)
    .WithRequired(entity => entity.ParentItem)
    .HasForeignKey(entity => entity.ParentItemId);

EDIT: extended answer.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Item>()
        .HasOptional(entity => entity.LinkedItem)
        .WithRequired(entity => entity.Item);

    modelBuilder.Entity<Item>()
        .HasMany(entity => entity.ChildItems)
        .WithRequired(entity => entity.ParentItem)
        .HasForeignKey(entity => entity.ParentItemId);
}

[Table("Item")]
public class Item
{
    [Key]
    public int ItemId { get; set; }

    public virtual ICollection<LinkedItem> ChildItems { get; set; }

    public virtual LinkedItem LinkedItem { get; set; }
}

[Table("LinkedItem")]
public class LinkedItem
{
    [Key]
    public int ItemId { get; set; }

    public int ParentItemId { get; set; }

    public virtual Item Item { get; set; }

    public virtual Item ParentItem { get; set; }
}

This gets me the results with the test tables I set up: