bcquality/microsoft/knowledge/style/fixed-choice-set-must-use-enum-not-integer.md

bc-version	domain	keywords	technologies	countries	application-area
all	style	enum option integer magic-number variable-typing field-typing	al	w1	all

A fixed set of named choices must use Enum, not a raw Integer

Contributions welcome — open a PR to refine or extend this article.

Description

When a variable or field can only take on a fixed set of more than two named, mutually exclusive states — a difficulty level, a document type, a processing status — it should be typed as Enum (or Option when extending an object that still uses the legacy type). Representing that same state as a plain Integer and tracking the meaning of each value in a comment or in a developer's head is a magic-number anti-pattern: the compiler cannot catch an out-of-range value, and branches read as opaque numbers instead of names. This is distinct from a true two-state choice, which should be Boolean rather than an enumeration — the line is the state count.

Best Practice

Declare an Enum with named values and branch on the enum value, not a raw number.

See sample: fixed-choice-set-must-use-enum-not-integer.good.al.

Anti Pattern

Using a plain Integer field with the meaning of each value tracked only in a comment pushes the documentation of the states into something the compiler cannot check and a future maintainer cannot rely on.

See sample: fixed-choice-set-must-use-enum-not-integer.bad.al.