Question

it is possible to be done using EF5?

X has many Y
Y has one X (one for many relationship)

however, Y has a second X that has no relation with the first X

is this possible?

public class X
{
    public int Id { get; set; }
    public List<Y> Ys { get; set; }
}

public class Y
{
    public int Id { get; set; }

    public int id_X { get; set; }
    [ForeignKey("id_X")]
    public X X { get; set; }

    public int id_X2 { get; set; }
    [ForeignKey("id_X2")]
    public X X2 { get; set; }
}

---

did not work.

The code looked like this.

class Program
{
    static void Main(string[] args)
    {
        using (var context = new context())
        {
            var x = context.X.FirstOrDefault();
        }
    }
}

public class context : DbContext
{
    public context()
        : base(@"server=localhost\ALTAIRNOTESTI; uid=sa; pwd=13509; database=DDD")
    {

    }
    public DbSet<X> X { get; set; }
    public DbSet<Y> Y { get; set; }
}

public class X
{
    [Required, Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public List<Y> Ys { get; set; }
}

public class Y
{
    [Required, Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public int id_X { get; set; }
    [ForeignKey("id_X")]
    [InverseProperty("Ys")]
    public X X { get; set; }

    public int id_X2 { get; set; }
    [ForeignKey("id_X2")]
    public X X2 { get; set; }
}

Answer 1

Yes, it’s possible, but you need to tell EF that X.Ys and Y.X (and not Y.X2) belong together in a single one-to-many relationship, for example by using the InverseProperty attribute:

[ForeignKey("id_X")]
[InverseProperty("Ys")]
public X X { get; set; }