michaelalber/dotnet-architecture-checklist

.NET / Blazor Architecture Checklist

"A checklist cannot fly a plane, but a pilot cannot fly safely without one." — Atul Gawande

Core Philosophy

Shared across the dotnet / python / php / rust architecture checklists — same values, language-specific checks.

| # | Value | What it means | |---|-------|---------------| | 1 | Detect before judge | Determine version/framework/structure before applying any item; context decides what is idiomatic. | | 2 | Evidence over opinion | Every finding cites file:line and the offending pattern. "Handlers are coupled" is not a finding; "OrderHandler.cs:12 inherits BaseCrudHandler<T>" is. | | 3 | Feature cohesion | Organized by business capability (feature folders), not technical layer. Cross-feature imports are a violation. | | 4 | Dependencies point inward | Domain logic does not depend on infrastructure; entities do not leak across API boundaries (anti-corruption layers). | | 5 | Explicit error handling | Failures handled at the right layer (pipeline behaviors); no silent swallowing; errors carry diagnostic context. | | 6 | Config & secrets hygiene | No hardcoded secrets; configuration via IOptions<T>; no secrets in WASM bundles. | | 7 | Version awareness | Recommendations are gated to the detected <TargetFramework>; never suggest an API absent from that version. | | 8 | Tests gate change | Untested code is a finding; high-risk handlers without tests are prioritized. | | 9 | Graded, actionable output | A letter grade (A–F) from counted findings, plus prioritized, version-correct recommendations. |

Workflow

Shared skeleton: DETECT → SCAN → REPORT → RECOMMEND.

DETECT     Target framework (grep <TargetFramework> in all .csproj; global.json/Directory.Build.props),
           hosting model (Program.cs render modes: Server/WASM/Auto; or controller Web API), and —
           CRITICAL — the ARCHITECTURE STYLE: layered/N-tier controllers vs. vertical-slice CQRS vs.
           mixed (see references/layered-ntier.md for the style-detection grep). Then CQRS library
           (FreeMediator vs MediatR), Mapster, and Telerik usage. The detected style selects which
           checklist branch is authoritative. If the framework or style is unclear, ask — never assume
           .NET 10 or vertical-slice.

SCAN       Run the checklist branch for the DETECTED style — the Vertical-Slice/CQRS branch (table below)
           OR the Layered/N-tier Controller branch (references/layered-ntier.md) — section by section,
           cross-referencing references/red-flags.md. Gather evidence with grep and dotnet build/analyzers.
           Every violation becomes a finding with file:line and a severity (critical/high/medium/low).

REPORT     Emit the graded report (Output Template). Grade = function of counted findings.

RECOMMEND  Prioritize: critical → quick wins → modernization. Version-gate every recommendation; provide
           upgrade paths for EOL frameworks (references/framework-detection.md).

.NET Checklist (language-specific)

Branch by detected style. Items 1–2 are style-specific — apply the row matching the project. Items 3–9 apply to both styles (item 3 only when a mediator is present).

| # | Check | Severity | |---|-------|----------| | 1 | Architectural coherence — the project follows its OWN chosen style consistently: vertical-slice → features by capability, no cross-feature imports; layered/N-tier → clean layer boundaries (Controllers → Services → Data), dependencies point inward, no layer-skipping. The finding is incoherence or a leaky boundary, never the choice of style. | Critical | | 2 | Controller / handler discipline — vertical-slice → each handler is a sealed standalone IRequestHandler<TReq,TRes>, no base handlers, thin endpoints that only mediator.Send(). layered → thin controllers ([ApiController]/ControllerBase), no business logic or EF queries in actions, delegate to a service layer; DTOs at the boundary, no entity leakage. (Full layered branch: references/layered-ntier.md) | Critical | | 3 | Mediator pipeline (CQRS projects only) — FreeMediator preferred (MediatR flagged for migration); validation/logging/exception/transaction behaviors registered in order. Skip for layered projects — do not flag the absence of a mediator. | Critical | | 4 | EF Core lifetime — DbContext scoped to the hosting model (singleton = Critical in Blazor Server); async all the way; no N+1 | Critical | | 5 | Framework health — EOL frameworks (.NET Core 3.1, 5, 7, 9) flagged Critical; .NET Framework 4.x gets an upgrade-path assessment | Critical | | 6 | Mapster discipline (when detected) — TypeAdapterConfig configured at startup; queries use ProjectToType<>() not ToList().Adapt() | High | | 7 | Shared kernel — official shared packages, version consistency, no duplicate entity definitions | High | | 8 | Config & secrets — IOptions<T>/IOptionsSnapshot<T>; no hardcoded secrets; WASM bundles secret-free | High | | 9 | Telerik (when detected) — Grid Data on large datasets paged/virtualized; component version alignment | High |

Layered/N-tier controller branch: layered & n-tier · CQRS patterns: cqrs patterns · framework upgrade paths: framework detection · anti-patterns: red flags. Full section-by-section list: review checklist.

State Block

<arch-checklist-state>
language: dotnet
mode: DETECT | SCAN | REPORT | RECOMMEND | COMPLETE
architecture_style: layered-controllers | vertical-slice-cqrs | mixed
detected: [target_framework | hosting_model | cqrs_lib | mapster:y/n | telerik:y/n | tests:y/n]
issues_found: [critical:N high:N medium:N low:N]
last_action: [what was just done]
next_action: [what should happen next]
</arch-checklist-state>

Output Template

Shared across all four architecture checklists.

## Architecture Checklist: [solution] (.NET)
**Framework**: [version] | **Style**: [Layered-Controllers/Vertical-Slice-CQRS/Mixed] | **Hosting**: [Server/WASM/Auto/Web API] | **CQRS**: [FreeMediator/MediatR/None] | **Tests**: [yes/no]

| Section | Pass | Fail | Warn |
|---------|------|------|------|
| Coherence / Controllers-Handlers / Pipeline / EF / Framework / Config / Telerik | … | … | … |

### Grade: [A–F]
Grading: **A** 0 crit/0 high/≤3 med · **B** 0 crit/≤2 high · **C** 0 crit, gaps in one area ·
**D** 1+ crit · **F** fundamental problems (EOL framework, singleton DbContext, missing auth; *vertical-slice:*
base-handler hierarchy; *layered:* business logic + EF queries in controllers). Grade against the detected
style — a coherent layered controller API with clean boundaries is an A.

| Severity | Location | Finding | Recommendation |
|----------|----------|---------|----------------|
| CRITICAL | file:line | [pattern] | [version-gated fix] |

**Quick wins**: [low-effort, high-impact] · **Modernization**: [larger items with effort estimate]

AI Discipline Rules

• Detect framework, hosting model, AND architecture style first. Recommending Interactive Auto to a .NET 6 project, Server patterns to a WASM app, or vertical-slice/CQRS to a layered controller API produces invalid findings. The style decides which branch is authoritative.
• Grade against the project's own style — never penalize the choice of style. A coherent layered controller API is an A, not a C "because it isn't vertical slice." The violations are incoherence and leaky boundaries (business logic in controllers, layer-skipping, entity leakage), not the absence of a mediator.
• Apply the right discipline check per style. Vertical-slice: a base-handler hierarchy (grep -r "class.*Handler.*:.*Base") is the critical structural problem to report first. Layered: business logic or EF queries inside controller actions (grep -rA10 "ActionResult" --include="*Controller.cs") is the equivalent critical finding.
• Never recommend a cross-style rewrite as a checklist finding. Do not tell a layered project to adopt CQRS, or a vertical-slice project to adopt repositories/layers. Flag any style change as a separate, optional migration with an effort estimate.
• Architecture, not security. Vulnerability findings belong to dotnet-security-review — note them and route there.

Integration with Other Skills

• architecture-review — When the grade is D/F, escalate to the Socratic critic: this checklist finds what is wrong; architecture-review builds why.
• dotnet-security-review — Companion for the security dimension (OWASP, Telerik, deserialization).
• dotnet-vertical-slice — Correct-pattern reference when a vertical-slice/CQRS project flags structural violations.
• dotnet-controller-api-scaffolder — Correct-pattern reference when a layered controller API flags structural violations (fat controllers, entity leakage, inconsistent conventions).
• ef-migration-manager — For EF Core lifetime/migration findings.
• legacy-migration-analyzer — When EOL/.NET Framework is detected, for a phased upgrade plan.
• tdd — Methodology for adding tests the checklist flags as missing.
• python / php / rust-architecture-checklist — Sibling skills sharing this exact Core Values + workflow + output.