ASP.net MVC Table relationships

我是MVC ASP.net 新手，这是我第一次尝试。我设计了一个带有关系表的小网站。（为了简短起见，我删除了一些不相关的字段）

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)

我相信这是不言自明的。 尝试为其创建以下模型时：

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; }
}

问题是在运行站点时，我收到异常无效的对象名称dbo.Divisions错误指向控制器中的返回值

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

任何帮助将不胜感激！