Build a Library with Deepstaging¶

You're going to build a library management system — two separate contexts that talk to each other through events, with a REST API, background jobs, full-text search, and tests. Everything runs in-memory. No database, no message broker, no Docker. Just dotnet run.

What You'll Build¶

Two contexts, a shared contracts project, and a test project:

Library/
├── src/
│   ├── Library.Contracts/     # Shared IDs and integration events
│   ├── Library.Catalog/       # Books, authors, search
│   └── Library.Lending/       # Patrons, loans, holds, overdue checks
└── test/
    └── Library.Tests/         # Tests for both contexts

┌──────────┐   integration    ┌──────────┐
│ Catalog  │◄──── events ────►│ Lending  │
└──────────┘                  └──────────┘
       ▲                            ▲
       └────── Library.Contracts ───┘

Catalog knows about books. Lending knows about patrons and loans. When someone borrows a book, Lending tells Catalog to update the inventory. They never reference each other directly — just events flowing through Contracts.

Chapters¶

#	Chapter	What You'll Learn	What You'll Build
1	Project Setup	`[TypedId]`, `[StoredEntity]`, `[DataStore]`	IDs, Book entity, CatalogStore
2	Effects & Runtime	`[Runtime]`, `Eff<RT,T>`, testing	CatalogRuntime, first test
3	Commands & Queries	`[DispatchModule]`, validation, search	AddBook, SearchBooks
4	Adding a REST API	`[RestApi]`, `[RateLimit]`, OpenAPI	Catalog endpoints
5	The Lending Context	Second runtime, `[Idempotent]`	BorrowBook, ReturnBook
6	Domain Events	`[EventQueue]`, in-process events	Loan count tracking
7	Jobs	`[BackgroundJob]`, `[Schedule]`	Overdue loan checker
8	Integration Events	`[IntegrationEvents]`, cross-context flow	Inventory sync
9	What's Next	Where to go from here	—

Tests are part of development

Each chapter includes tests as you go — not bolted on at the end.

Prerequisites¶

.NET 10 SDK
An IDE — Visual Studio, Rider, or VS Code with C# Dev Kit
Basic familiarity with C# and dependency injection

That's it. No Docker. No cloud accounts. No infrastructure.

The Pattern¶

Every Deepstaging feature works the same way:

Attribute → Source Generator → Generated C# → Compiled into your app

No reflection. No runtime magic. Everything the generator produces is visible in your generated/ folder — you can read it, debug into it, and navigate it in your IDE.

Reference implementation

The complete working code lives in the Library sample. Use it to check your work or skip ahead.

Get started → Project Setup