Required validating property of another object

Question

I have the following properties, however when I will validate via Modelstate.Isvalid returns that the description of the user group to be informed that it is User too, but the problem is that I am asking for the database itself to generate the key. How do I not present these inconsistencies?
Groupuser is being filled with a Dropdownlist.

     [Key]
     [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
      public int UsuarioId { get; set; }

    [Required(ErrorMessage = "Nome do usuário deve ser informado")]
    public string UsuarioDeAcesso { get; set; }

    [Required(ErrorMessage = "Senha do usuário deve ser informada")]
    public string SenhaDeAcesso { get; set; }

    [Required(ErrorMessage = "Grupo deve ser selecionado")]
    public int GrupoDeUsuarioId { get; set; }
    [Required(ErrorMessage = "Grupo deve ser selecionado")]
    public GrupoDeUsuario GrupoDeUsuario { get; set; }

Answer 1

Don’t use this:

[Required(ErrorMessage = "Grupo deve ser selecionado")]
public GrupoDeUsuario GrupoDeUsuario { get; set; }

Navigation properties are complex entities. You should only keep this validation completed below, because this is the important element of the validation, and not the dependent object:

[Required(ErrorMessage = "Grupo deve ser selecionado")]
public int GrupoDeUsuarioId { get; set; }