c# - ASP.net MVC テーブルの関係

Question

ASP.net MVC は初めてで、これが初めての試みです。リレーショナル テーブルを使用して小さなサイトを設計しています。（簡潔にするために、無関係なフィールドをいくつか削除しました）

Items:

• Id int (PK)
• description nvarchar(50)
• divisionid nchar(2) FK
• categoryid nchar(6) FK

Division

• code nchar(2) PK
• description nvarchar(50)

Category

• code nchar(6) PK
• description nvarchar(50)

自明だと思います。以下のモデルを作成しようとすると：

public class Item
{
    [Key]
    [Display(Name="Id")]
    public int Id { get; set; }

    [Required(ErrorMessage="Description is required")]
    [Display(Name = "Description")]
    [StringLength(50, ErrorMessage = "Description must not be more than 50 characters long")]
    public string Description { get; set; }

    [Display(Name = "Division")]
    [StringLength(2)]
    public string DivisionId { get; set; }        

    [Display(Name = "Category")]
    [StringLength(6)]        

    [ForeignKey("DivisionId")]
    public virtual Division division { get; set; }
    [ForeignKey("CategoryId")]
    public virtual Category Category { get; set; }

}

public class Division
{
    [Key]
    [Display(Name = "Code")]
    [StringLength(2, ErrorMessage = "Code must be 2 char.")]
    public string Code { get; set; }

    [Display(Name = "Description")]
    [Required(ErrorMessage = "Description is required")]
    [StringLength(50,ErrorMessage="Description must not be more than 50 characters long")]
    public string Description { get; set; }

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

public class Category
{
    [Key]
    [Display(Name = "Code")]
    [StringLength(6, ErrorMessage = "Code must be 6 char.")]
    public string Code { get; set; }

    [Display(Name = "Description")]
    [Required(ErrorMessage = "Description is required")]
    [StringLength(50, ErrorMessage = "Description must not be more than 50 characters long")]
    public string Description { get; set; }

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

問題は、サイトを実行しているときに、無効なオブジェクト名の例外がdbo.Divisions 発生し、コントローラーの戻り値を指すエラーが発生することです

    Line 20:         {
    Line 21:             var items = db.Items.Include(i => i.division).Include(i => i.Category);
    Line 22:             return View(items.ToList());
    Line 23:         }

どんな助けでも大歓迎です！