What is the difference between First and FirstOrDefault?
PICTURE THIS: RAG CHATBOT
Simple meaning
First throws if the sequence is empty.
WHY — LINQ instead of guessing?
Why interviewers care about LINQ:
contrast on LINQ, not two memorised paragraphs.
the developer, then one case where picking wrong hurts.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1First throws if the
sequence is empty.
- 2Why it exists
FirstOrDefault returns default(T) instead.
- 3I prefer FirstOrDefault when
empty is normal, then check for null or default.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
First throws if the sequence is empty. FirstOrDefault returns default(T) instead.