OptimisticConcurrencyException when persisting related entry

Question

FIXED

I need to read the documentation to see why it's fix the error, but adding

[DatabaseGenerated(DatabaseGeneratedOption.Identity)]

before each key that is AUTO INCREMENT fix the problem.

.

sorry about that, i read allot of questions like this I am doing, but i can't figure out what's happening...

I'm making only one request, so i'ts not concurrency ... I have 3 entitys

FIRST:

[Table("banco_bar.mesa")]
public partial class mesa
{       
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public mesa()
    {
        mesatempedido = new HashSet<mesatempedido>();
        pedidomesa = new HashSet<pedidomesa>();
    }

    [Key]
    public int idMesa { get; set; }

    [Required]
    [StringLength(100)]
    public string nomeMesa { get; set; } 


    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<mesatempedido> mesatempedido { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<pedidomesa> pedidomesa { get; set; }
}

SECOND:

[Table("banco_bar.mesatempedido")]
public partial class mesatempedido
{
    [Key]
    [Column(Order = 0)]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int idMesa { get; set; }

    [Key]
    [Column(Order = 1)]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int idPedidoMesa { get; set; }

    [Key]
    [Column(Order = 2)]
    [StringLength(15)]
    public string senhaPedido { get; set; }

    [Key]
    [Column(Order = 3)]
    public bool requisitadoFechamento { get; set; }

    public virtual mesa mesa { get; set; }

    public virtual pedidomesa pedidomesa { get; set; }
}

THIRD:

[Table("banco_bar.pedidomesa")]
public partial class pedidomesa
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public pedidomesa()
    {
        itenspedido = new HashSet<itenspedido>();
        mesatempedido = new HashSet<mesatempedido>();
    }

    [Key]
    public int idPedidoMesa { get; set; }

    public int? idMesa { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public DateTime dataAbertura { get; set; }

    public DateTime? dataFechamento { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<itenspedido> itenspedido { get; set; }

    public virtual mesa mesa { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<mesatempedido> mesatempedido { get; set; }
}

Doesn't matter how I try to add the SECOND or the THIRD Entity, i aways get

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=472540 for information on understanding and handling optimistic concurrency exceptions.

What I am doing wrong here?

var db = new Models.ModelContext();
var mesa = db.mesa.Where(m => m.idMesa == mesaId).FirstOrDefault();
if (mesa == null)
{
    return new HttpUnauthorizedResult();
}else
{
    pedidomesa pm = db.pedidomesa.Add(new pedidomesa { mesa = mesa });

    mesatempedido mtp = db.mesatempedido.Add(new mesatempedido { mesa = mesa, pedidomesa = pm, senhaPedido="bario" });

   db.SaveChanges();
   return Json(new { pm, mtp });
}

Note: If i just try

db.mesa.Add(new Mesa(){nomeMesa ="asih"}); 
db.SaveChanges();

it's persist the new entity.

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