Can you shorten multiple chained null checks in C#?

Question

I have just started learning C#. I'm making a game mod for Rimworld and cannot modify the pawn code. Apparently, any of the chained objects may be null. Is there a better way to bail out of the method than what I've done?

Thank you.

    private void cleanseParadoxicalMemories(Pawn pawn, Dictionary<string, string> knownPawnIDs)
    {
        if (pawn.needs == null || pawn.needs.mood == null || pawn.needs.mood.thoughts == null || pawn.needs.mood.thoughts.memories == null)
        {
            return;
        }

        // Remove any crazy-making memories from a now-invalid timeline due to traveling across an Einstein-Rosen bridge
        // (basically, selective amnesia about everyone not going with us.)
        foreach (var paradox in pawn.needs.mood.thoughts.memories.Memories.ToList())
        {
            if (paradox.otherPawn != null)
            {
                pawn.needs.mood.thoughts.memories.RemoveMemory(paradox);
            }
        }
    }

I think you could just use `?.` here, at least in the if. `pawn.needs?.mood?.thoughts?.memories` will be null if any of those are. If I’m not entirely mistaken `foreach` doesn’t like nulls so cant put the whole thing inside it — Sami Kuhmonen, Aug 09 '20 at 15:48
Or `foreach(var paradox in (pawn?.needs?.mood?.thoughts?.memories?.Memories ?? Enumerable.Empty()).ToList())` — pinkfloydx33, Aug 09 '20 at 17:12

score 3 · Answer 1 · answered Aug 09 '20 at 15:49

You can use null conditional operator ?. to achieve this :

private void cleanseParadoxicalMemories(Pawn pawn, Dictionary<string, string> knownPawnIDs)
{
   if (pawn?.needs?.mood?.thoughts?.memories == null)
   {
      return;
   }

   // Remove any crazy-making memories from a now-invalid timeline due to traveling across an Einstein-Rosen bridge
   // (basically, selective amnesia about everyone not going with us.)
   foreach (var paradox in pawn.needs.mood.thoughts.memories.Memories.ToList())
   {
      if (paradox.otherPawn != null)
      {
         pawn.needs.mood.thoughts.memories.RemoveMemory(paradox);
      }
   }

Can you shorten multiple chained null checks in C#?

1 Answers1