<objective>
SOLID C# enforces a modular architecture for C# 14/.NET 10 projects: every feature lives under `Modules/[Feature]/` (Controllers, Services, Repositories, Contracts, Models) with shared code centralized in `Core/`, contracts are mandatory and live only in `Contracts/` directories, and interfaces stay small (1-3 members). File size is governed by the hook ceiling `FUSE_SOLID_MAX_LINES`; controllers stay thin.
Before writing any new code it requires a DRY check -- grep the codebase and Core/Services/Core/Contracts for existing logic to reuse before creating something new. See principles.md for the 5 SOLID principles and patterns.md for directory layout, testing, and record usage.
</objective>
SOLID C# - Modular Architecture
Agent Workflow (MANDATORY)
Before ANY implementation, spawn 3 agents in parallel, one Agent call each with a name:
- fuse-ai-pilot:explore-codebase - Analyze existing architecture
- fuse-ai-pilot:research-expert - Verify .NET docs via Context7
- fuse-ai-pilot:sniper - Post-implementation validation
DRY - Reuse Before Creating (MANDATORY)
Before writing ANY new code:
- Grep the codebase for similar interfaces, services, or logic
- Check shared locations:
Core/Services/, Core/Contracts/
- If similar code exists -> extend/reuse instead of duplicate
- If code will be used by 2+ features -> create it in
Core/
Architecture (Modules MANDATORY)
| Layer |
Location |
| Controllers |
Modules/[Feature]/Controllers/ |
| Services |
Modules/[Feature]/Services/ |
| Repositories |
Modules/[Feature]/Repositories/ |
| Contracts |
Modules/[Feature]/Contracts/ |
| Models |
Modules/[Feature]/Models/ |
| Shared |
Core/{Services,Contracts,Models}/ |
NEVER use flat structure - always Modules/[Feature]/
Critical Rules (MANDATORY)
| Rule |
Value |
| File limit |
FUSE_SOLID_MAX_LINES |
| Controllers |
Thin, delegate to services |
| Interfaces |
Contracts/ directory ONLY |
| XML docs |
Every public member documented |
| DI |
Use Microsoft.Extensions.DependencyInjection |
| Small interfaces |
1-3 members max |
| Records |
Prefer record for DTOs and value objects |
Reference Guide
| Topic |
Reference |
When to consult |
| SOLID Principles |
principles.md |
Quick reference for all 5 principles |
| Patterns & Structure |
patterns.md |
Directory layout, testing, records |
Forbidden
| Anti-Pattern |
Fix |
Files over FUSE_SOLID_MAX_LINES |
Split by responsibility |
| Interfaces in impl files |
Move to Contracts/ directory |
| Fat interfaces (4+ members) |
Split into focused interfaces |
| Flat project structure |
Use Modules/[Feature]/ |
new for dependencies |
Use constructor injection + DI |
| Service Locator pattern |
Use constructor injection |