Only parameterless constructors and initializers are supported in LINQ to Entities

Question

I have this error in this linq expression :

var naleznosci = (from nalTmp in db.Naleznosci
                              where nalTmp.idDziecko == idDziec
           


        

Answer 1

Sorry for being late to the party, but I after finding this, I thought this should be shared as it's the cleanest, fastest and also memory-saving implementation I could find.

Adapted to your example, you'd write:

public static IQueryable ToPayments(this IQueryable source)
{
  Expression> createPayments = naleznosci => new Payments
  {
    Imie = source.Dziecko.Imie,
    Nazwisko = source.Dziecko.Nazwisko,
    Nazwa= source.Miesiace.Nazwa,
    Kwota = source.Kwota,
    NazwaRodzajuOplaty = source.RodzajeOplat.NazwaRodzajuOplaty,
    NazwaTypuOplaty = source.RodzajeOplat.TypyOplat.NazwaTypuOplaty,
    DataRozliczenia = source.DataRozliczenia,
    TerminPlatnosci = source.TerminPlatnosci,
  };

  return source.Select(createPayments);
}

The big advantages here (as Damien Guard pointed out in the comments at the link) are:

• Safes you from using initialization pattern on each occurrence.
• Usage via var foo = createPayments(bar); as well as usage via myIQueryable.ToPayments() possible.