EF6 and NPGSQL : Foreign key breach error

Question

Good afternoon ! I’m new to ASP.NET and EF6. I used to develop in PHP.

I created a project (ASP.NET MVC) using EF6 and NPGSQL. I got a little bit when creating relationships between two tables but it worked. The persona table will have several countries (1:n). It follows SQL, Model and context.

SQL:

 CREATE TABLE pais(
  idpais character(3) NOT NULL,
  nomepais character varying(100) NOT NULL,
  CONSTRAINT pk_pais PRIMARY KEY (idpais),
  CONSTRAINT ix_nomepais UNIQUE (nomepais)
)

CREATE TABLE persona
(
  idpersona serial NOT NULL,
  nomepers character varying(100) NOT NULL,
  idpaispers character(3),
  CONSTRAINT pk_persona PRIMARY KEY (idpersona),
  CONSTRAINT fk_perspais FOREIGN KEY (idpaispers)
      REFERENCES pais (idpais) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT ix_nomepers UNIQUE (nomepers)
)

Model Pais

[Table("pais",Schema="public")]
public class Pais
{
    public Pais()
    {
        this.Persona = new HashSet<Persona>();
    }
    [Key]
    [Column("idpais")]
    [Display(Name = "Sigla")]
    [DataType(DataType.Text)]
    [StringLength(3)]
    [Required]
    public string IDPais { get; set; }

    [Column("nomepais")]
    [Display(Name = "Nome")]
    [DataType(DataType.Text)]
    [StringLength(100)]
    [Index("ix_nomepais",IsUnique=true)]
    [Required]
    public string nomePais { get; set; }

    public virtual ICollection<Persona> Persona { get; set; }
}

Model Persona :

    [Table("persona", Schema="public")]
public class Persona
{
    [Key]
    [Column("idpersona")]
    public int IDPersona { get; set; }

    [Column("nomepers")]
    [Display(Name = "Nome")]
    [DataType(DataType.Text)]
    [StringLength(100)]
    [Index("ix_nomepers", IsUnique = true)]
    [Required]
    public string nomePers { get; set; }

    [Column("idpaispers")]
    [Display(Name = "País")]
    [DataType(DataType.Text)]
    [StringLength(3)]
    public string idpaisPers { get; set; }
    public virtual Pais Pais { get; set; }

}

Context:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Persona>()
                .HasRequired<Pais>(p => p.Pais)
                .WithMany(e => e.Persona)
                .HasForeignKey(e => e.idpaisPers);
}

When it comes to including a "persona", I purposely specify a country that is not registered, generating a foreign key violation error of Postgres. But shouldn’t EF validate before ? Was I wrong or should I include a validation to prevent this error ? Thank you in advance who can help.

Answer 1

When it comes to including a "persona", I purposely specify a country that is not registered, generating a foreign key violation error of Postgres. But the RU should not do the validation before?

No, the Entity Framework does not perform foreign key validation. Validation has to be done in the Controller.

I missed something or should include a validation so that this error does not occur?

You can capture the exception or develop a preventive code in your Controller to check if it makes sense to assign Id of the country in question. This is done by business rules in the Controller, that is the layer responsible for harmonizing the relations between Models.