ErrorMapping

What one exception becomes on the wire, returned by IExceptionMapper and consumed by the handler that owns it. It carries the whole presentation decision for a failure, which is what keeps the exception itself free of HTTP and localization detail.

Fields

StatusCode: int
Status the response is sent with, and the value the handler passes to the response writer so the error body's Code repeats it.

Code: string
Machine-readable identifier the client branches on, such as invalid_credentials. Treat it as public API, because renaming it breaks consumers without breaking a build.

MessageKey: string
Key resolved through the message resolver for the description. A key no message file defines reaches the client verbatim, so it should read as a key rather than as prose.

MessageParameters: IReadOnlyList<object?>
Values substituted into the resolved template by position, as {0} onwards. Pass an empty list when the message takes none.

Type signature

public sealed record ErrorMapping
{
    public required int StatusCode { get; init; }
    public required string Code { get; init; }
    public required string MessageKey { get; init; }
    public required IReadOnlyList<object?> MessageParameters { get; init; }
}