ASP.NET Core Web API Interview Question #49
How should null and empty results be handled in API responses?
DTOs, Model Binding, Validation & API Responses Junior Beginner
Quick Interview Answer
A request for one specific resource normally returns 404 when that resource does not exist. A valid collection query that finds no matching records normally returns 200 with an empty collection rather than 404.
Detailed Explanation
A request for one specific resource normally returns 404 when that resource does not exist. A valid collection query that finds no matching records normally returns 200 with an empty collection rather than 404.
This distinction gives clients predictable semantics: the collection resource exists even when it currently contains zero matching items.
Code Example
// Single resource:
if (product == null)
return NotFound();
// Collection:
return Ok(Array.Empty<ProductResponse>());