private void AgregarComision(Commission  comision)
 {
     if (ExisteComision(comision))
         throw new ArgumentException("Comision ya existe");
     db.Commissions.Add(comision);
 }
 public bool ExisteComision(Commission comision)
 {
     if (comision == null)
         return false;
     return (db.Commissions.SingleOrDefault(c => c.ID == comision.ID ||
         c.Name == comision.Name) != null);
 }