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📜 WAYPOINT LESSON

Checkpoint — The Generic Data Store

⭐⭐ intermediate⏳ 22 min read📍 Lesson 103 of 265

Build a constrained generic store with ordering, defaults, and variance-safe surfaces.

The gate (mini-build)

A DataStore<TId, TEntity> where TEntity : Entity<TId> and TId : IComparable<TId>:

  • Add(TEntity) / Get(TId) (null when missing) / Delete(TId) (bool).
  • AllOrdered() returns entities ordered by Id — the constraint makes the ordering possible without casts.
  • FirstMatching(Predicate<TEntity>) returns TEntity? (default when none).

Supporting type: public abstract class Entity<TId> { public abstract TId Id { get; } }. The graded test drives two different entity types through one store type — the whole point of generic design.