What is dependency injection in ASP.NET Core?
PICTURE THIS: DATA SPLIT
Fit on train, tune on val, report on test once.
Simple meaning
The built-in container registers services with lifetimes: transient, scoped, singleton.
WHY — ASP.NET instead of guessing?
Why interviewers care about ASP.NET:
who only read docs from people who shipped.
and tied to .NET work.
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:
- 1The built-in container registers
services with lifetimes: transient, scoped, singleton.
- 2Why it exists
Controllers receive dependencies via constructor.
- 3It keeps code testable
and modular.
- 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
The built-in container registers services with lifetimes: transient, scoped, singleton. Controllers receive dependencies via constructor.