What is the difference between const and readonly?
PICTURE THIS: RAG CHATBOT
Simple meaning
Const is a compile-time literal baked into callers.
WHY — C# instead of guessing?
Why interviewers care about C#:
contrast on C#, 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:
- 1Const is a compile-time
literal baked into callers.
- 2Readonly can be set
in the constructor and can be a runtime value.
- 3I use const for
true constants like a magic number, and readonly for configuration that is fixed after construction.
- 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
Const is a compile-time literal baked into callers. Readonly can be set in the constructor and can be a runtime value.