Check Nullable for object insde LinQ to Sql code

Question

I am using this example Linq code:

from objpath in _context.PathModel
    join objOriginalStation in _context.StationModel 
        on objpath.IdStazioneOrigine equals objOriginalStation.IDStazione
    join objDesttinationStation in _context.StationModel 
        on objpath.IdStazioneDestinazione equals objDesttinationStation.IDStazione
    join objVia1Station in _context.StationModel 
        on objpath.IdVia1 equals objVia1Station.IDStazione
    join objVia2Station in _context.StationModel 
        on objpath.IdVia2 equals objVia2Station.IDStazione
    select new NewPercorsiModel
    {
        IdPercorso = objpath.IdPercorso,
        IdSottorete = objpath.IdSottorete,
        Distanza = objpath.Distanza,
        IdStazioneDestinazione = objpath.IdStazioneDestinazione,
        IdStazioneOrigine = objpath.IdStazioneDestinazione,
        IdVia1 = objpath.IdVia1,
        IdVia2 = objpath.IdVia2,
        Versione = objpath.Versione ?? string.Empty,
        StazioneOrigineName = objOriginalStation.NomeStazione,
        StazioneDestinazioneName = objDesttinationStation.NomeStazione,
        Via1Name = objVia1Station.NomeStazione,
        Via2Name = objVia2Station.NomeStazione ?? string.Empty
    };

First of all my question is that, have I a better solution to improve my code?

and second and important my question is that how could I check nullable for my objects(for example for objVia2Station) because when they are null I don't have all my records but I don't have any error also.

Answer 1

you can use "DefaultIfEmpty()" after each join like this code

from objpath in _context.PathModel
join objOriginalStation in _context.StationModel 
    on objpath.IdStazioneOrigine equals objOriginalStation.IDStazione into object1
    from Ob1 in object1.DefaultIfEmpty()
join objDesttinationStation in _context.StationModel 
    on objpath.IdStazioneDestinazione equals objDesttinationStation.IDStazione into object2
    from Ob2 in object2.DefaultIfEmpty()
join objVia1Station in _context.StationModel 
    on objpath.IdVia1 equals objVia1Station.IDStazione into object3
    from Ob3 in object3.DefaultIfEmpty()
join objVia2Station in _context.StationModel 
    on objpath.IdVia2 equals objVia2Station.IDStazione into object4
    from Ob4 in object4.DefaultIfEmpty()
select new NewPercorsiModel
{
    IdPercorso = objpath.IdPercorso,
    IdSottorete = objpath.IdSottorete,
    Distanza = objpath.Distanza,
    IdStazioneDestinazione = objpath.IdStazioneDestinazione,
    IdStazioneOrigine = objpath.IdStazioneDestinazione,
    IdVia1 = objpath.IdVia1,
    IdVia2 = objpath.IdVia2,
    Versione = Ob1.Versione  ,
    StazioneOrigineName = objOriginalStation.NomeStazione,
    StazioneDestinazioneName = objDesttinationStation.NomeStazione,
    Via1Name = objVia1Station.NomeStazione,
    Via2Name = Ob4.NomeStazione  
};

this code in equal to "Left Outer Join", But I don't like it because we can use Inheritance Strategy in Entity Framework You should start receiving data when you encounter another table. like this:

var query = context.BaseTable.Select(x => new
         {
          x.Id,
          x.field1,
          x.field2,
          ..
          ..
          alias_name= x.ForeignTable== null ? "" : x.ForeignTable.Name
         });