ForeignKey attribute is not valid error

Question

Can you help me?

namespace mvcAmerica.Models
{
    public class ArtModels
    {     
        [Key]
        public int idArt { get; set; }

        [Required(ErrorMessage="Codigo del Articulo es Requerido")]
        public string co_art { get; set; }

        [Required]
        public string des_art { get; set; }

        [Required]
        public string modelo { get; set; }

        [Required]
        public string referencia { get; set; }

        [ForeignKey("LineaModels")]
        public int IdLinea { get; set; }

        public LineaModels Linea { get; set; }
    }

    public class LineaModels
    {        
        [Key]
        public int IdLinea { get; set; }

        [Required(ErrorMessage="Indique el Codigo")]
        public string co_lin { get; set; }

        [Required(ErrorMessage = "Indique la Descripción")]
        public string des_lin { get; set; }
    }
}

Error:

The ForeignKeyAttribute on property 'IdLinea' on type 'mvcAmerica.Models.ArtModels' is not valid. The navigation property 'LineaModels' was not found on the dependent type 'mvcAmerica.Models.ArtModels'. The Name value should be a valid navigation property name.

Answer 1

You need to change this:

[ForeignKey("LineaModels")]
public int IdLinea { get; set; }
public LineaModels Linea { get; set; }

To this:

[ForeignKey("Linea")]
public int IdLinea { get; set; }
public virtual LineaModels Linea { get; set; }

It needs to match the property name.

Edit

I've just created the following application with no problems:

    public class ArtModels
    {
        [Key]
        public int idArt { get; set; }
        [Required(ErrorMessage = "Codigo del Articulo es Requerido")]
        public string co_art { get; set; }
        [Required]
        public string des_art { get; set; }
        [Required]
        public string modelo { get; set; }
        [Required]
        public string referencia { get; set; }
        [ForeignKey("Linea")]
        public int IdLinea { get; set; }
        public virtual LineaModels Linea { get; set; }
    }

    public class LineaModels
    {
        [Key]
        public int IdLinea { get; set; }
        [Required(ErrorMessage = "Indique el Codigo")]
        public string co_lin { get; set; }
        [Required(ErrorMessage = "Indique la Descripción")]
        public string des_lin { get; set; }
    }

    public class AppContext : DbContext
    {
        public DbSet<ArtModels> ArtModelses { get; set; }
        public DbSet<LineaModels> LineaModelses { get; set; }
    }

So you must be missing something else?

Answer 2

You have to change this:

  [ForeignKey("LineaModels")]
  public int IdLinea { get; set; }

To this:

  [ForeignKey("Linea")]
  public int IdLinea { get; set; }

The ForeignKey name has to be the same as your navigation property (here Linea).