What is the difference between string and StringBuilder?
PICTURE THIS: RAG CHATBOT
Simple meaning
string is immutable so each change may allocate a new string.
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:
- 1string is immutable so
each change may allocate a new string.
- 2StringBuilder mutates a buffer
for many appends.
- 3I use StringBuilder in
loops that build text.
- 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
string is immutable so each change may allocate a new string. StringBuilder mutates a buffer for many appends.