Entity Framework FK error

Question

My code is returning the following error:

The property 'cartID' cannot be configured as a navigation property. The property must be a valid entity type and the property should have a non-abstract getter and setter. For collection properties the type must implement ICollection where T is a valid entity type.

My model is below:

[Table("ShoppingCarts")]
public class ShoppingCart 
{
    [Key]
    public string cartID { get; set; }

    public virtual ICollection<ShoppingCartItem> CartItems { get; set; }
    public DateTime? DateCreated { get; set; }
    public Guid UserID { get; set; }
}


[Table("ShoppingCartItems")]
public class ShoppingCartItem
{


    private string cartDisplayImg;

    [Key]
    [Display(Name = "Cart Item ID#")]
    public int cartItemID { get; set; }

    [Display(Name = "Cart ID")]
    [ForeignKey("cartID")]
    public string cartID { get; set; }
    [Required]
    public string itemTitle { get; set; }

    public int listingID { get; set; }
    public int sellerID { get; set; }
    [Required]
    public string sellerSKU { get; set; }
    [Required]
    public int Quantity { get; set; }
    public string itemType { get; set; }

    public string condition { get; set; }
    [Required]
    public decimal Price { get; set; }

    public string Make { get; set; }
    public string Model { get; set; }
    public string displayImgPath
    {

        get {
           cartDisplayImg = "http://www.example.com/Images/Phones/" + Make + "-" + Model + "-1.jpg";

           return cartDisplayImg;

        }

    }
    public decimal lineTotal
    {
        get {
            decimal cartLineTotal = Price * Quantity;
            return cartLineTotal; 
        }

    }

}

public class ShopingCartContext : DbContext
{

    public ShopingCartContext()
        : base("PHONEOUTLET_DBConnectionString")
    {
        Database.SetInitializer<ShopingCartContext>(new CreateDatabaseIfNotExists<ShopingCartContext>());

    }


    public DbSet<ShoppingCart> ShoppingCart { get; set; }
    public DbSet<ShoppingCartItem> ShoppingCartItems { get; set; }
}

I guess that is because cartID is a string? try to change it to int and add [DatabaseGenerated(DatabaseGeneratedOption.Identity)] after [Key] for auto generation. — nramirez, Apr 15 '15 at 17:19

ocuenca · Accepted Answer · 2015-04-15T18:13:26.737

6

The ForeignKey data annotation must be used on the FK property along with information telling it which navigation property represents the relationship it is a foreign key for:

[Table("ShoppingCartItems")]
public class ShoppingCartItem
{
   //..
   [Display(Name = "Cart ID")]
   [ForeignKey("Shoppingcart")]
   public string cartID { get; set; }
   public virtual ShoppingCart Shoppingcart { get; set; }
}

And alternatively, you can apply the ForeignKey annotation to the navigation property and tell it which property is the foreign key for the relationship:

[Table("ShoppingCartItems")]
public class ShoppingCartItem
{
   //..
   [Display(Name = "Cart ID")]
   public string cartID { get; set; }

   [ForeignKey("cartID")]
   public virtual ShoppingCart Shoppingcart { get; set; }
}

In addition, Code First has a set of rules that are applied to locate a foreign key property when it discovers a relationship. The conventions are based on the name of the property. The foreign key property will be discovered by convention if it is named [Target Type Key Name], [Target Type Name] + [Target Type Key Name], or [Navigation Property Name] + [Target Type Key Name]. If you use the ForeignKey data annotation these rules will be ignored because you are telling explicitly to EF what FK property you want to use.

edited Apr 15 '15 at 18:13

answered Apr 15 '15 at 17:29

ocuenca

38,548
11
89
102

I agree with this solution , although I recommend promoting EF code first conventions – IndieTech Solutions Apr 15 '15 at 17:31
1

I'm agree with you that is important to know these conventions, but I prefer to tell explicitly to EF which are my FK property using the `ForeignKey` data annotation or using Fluent Api. Anyway, I added these conventions in my answer – ocuenca Apr 15 '15 at 18:31
1

Voted up for your answer – IndieTech Solutions Apr 15 '15 at 18:32
The ForeignKeyAttribute on property 'cartID' on type 'MySite.Models.ShoppingCartItem' is not valid. The navigation property 'Shoppingcart' was not found on the dependent type 'MySite.Models.ShoppingCartItem'. The Name value should be a valid navigation property name. – user1698144 Apr 15 '15 at 20:35
Did you add the navigation property `ShoppingCart` on your `ShopingCartItem` entity?. Look the first example, I'm sure you forgot to add the `public virtual ShoppingCart Shoppingcart { get; set; }` – ocuenca Apr 15 '15 at 20:50

score 0 · Answer 2 · answered Apr 15 '15 at 17:20

0

Wouldn't the type for CartID have to be an integer and not a string? I'm not sure if this would fix your issue or not, but it seems like that is what the error message is talking about.

answered Apr 15 '15 at 17:20

mcloud313

37
6

That's not it. @mcloud you can create string PK using GUID() , it's easier. check out this conversation : http://stackoverflow.com/questions/1250716/why-not-always-use-guids-instead-of-integer-ids – IndieTech Solutions Apr 15 '15 at 17:24

IndieTech Solutions · Answer 3 · 2015-04-15T18:32:52.193

Try to follow EF code conventions so instead of this

    [Display(Name = "Cart ID")]
    [ForeignKey("cartID")]
    public string cartID { get; set; }

Try this

    [Display(Name = "Cart ID")]
    public string CartID { get; set; }
    public virtual ShoppingCart Shoppingcart { get; set; }

A common way to define one to many relationships in classes is to have a child collection in the one class and then a foreign key property along with a navigation property in the child class.

EDIT 1: Try to follow EF code conventions. Please refer to this article for more info :Code First Conventions

Entity Framework FK error

3 Answers3