How do you constrain a route parameter?
PICTURE THIS: DATA SPLIT
Fit on train, tune on val, report on test once.
Simple meaning
Constraints like {id:int} reject non-integers before the action runs.
WHY — Routing instead of guessing?
Why interviewers care about Routing:
question about Routing.
trade-offs, and what you would actually do on a .NET MVC project - not buzzwords.
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:
- 1Constraints like {id:int} reject
non-integers before the action runs.
- 2I use them so
a slug and an id do not collide.
- 3Custom constraints exist when
the rule is domain-specific.
- 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
Constraints like {id:int} reject non-integers before the action runs. I use them so a slug and an id do not collide.