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📜 WAYPOINT LESSON

Checkpoint — The Catalog Import/Export Engine

⭐⭐ intermediate⏳ 25 min read📍 Lesson 131 of 265

Combine options, converters, and boundary defense into one round-trip-safe catalog service.

The gate (mini-build)

A product catalog exchange — import, export, and transform:

  1. Export(IEnumerable<Product> products) → camelCase JSON array: [{"name":"bolt","price":0.5},...] (name string, price number).
  2. Import(string json) → products; tolerant of price as number OR string (via a custom converter); malformed JSON or a missing/empty name → InvalidOperationException("bad payload").
  3. Merge(string jsonA, string jsonB) → union by name (first wins), exported as Export would.

Product: record Product(string Name, decimal Price). Input JSON shape: {"products":[{"name":"bolt","price":0.5}]}.