# Why Can't the Dictionary Find Card 1042? Good Keys

Find a member's locker from the card scanned this morning, when both of the gym's branches have a member 1042: why the card object, the member number alone and equality on its own each fail, and how to make your own type a key that works in your language.

![Cheat sheet: Why Can't the Dictionary Find Card 1042? Good Keys](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/da7d66fb74d24f578a4063ef776be19f.webp)

- Category: Data Structures
- Level: Journeyman
- Tags: data structures, Dataclass, Hash Code, Immutable Object, Record Class, Record Type, Value Equality
- Updated: November 3, 2026

Source: https://www.ask-codey.com/cheat-sheets/ds-good-keys-cheat-sheet