Consistent API Errors with ProblemDetails in ASP.NET Core
In the world of API development, consistency is king. One of the most common areas where consistency breaks down is error handling. Different endpoints might return different JSON structures for a 404 Not Found versus a 500 Internal Server Error, forcing API consumers to write complex, brittle parsing logic.
ASP.NET Core provides a clean, built-in solution to this problem: the ProblemDetails middleware. By adopting this standard, you can ensure all your API’s error responses have a predictable, machine-readable shape.
What is Problem Details?
ProblemDetails is a specification defined in RFC 7807 that establishes a standard format for returning error information from an HTTP API. It’s essentially a contract for what an error response should look like.
A standard ProblemDetails object includes these key fields:
- type: A URI that identifies the problem type. This can link to documentation explaining the error.
- title: A short, human-readable summary of the problem.
- status: The HTTP status code generated by the server for this occurrence of the problem.
- detail: A human-readable explanation specific to this occurrence of the problem.
- instance: A URI that identifies the specific occurrence of the problem.
Here’s an example of what a ProblemDetails response looks like in JSON:
{
"type": "[https://tools.ietf.org/html/rfc7231#section-6.5.4](https://tools.ietf.org/html/rfc7231#section-6.5.4)",
"title": "Not Found", …