This week in Cursor + .NET — 7 rules (week ending June 14, 2026)

*Every weekday a single, opinionated rule for senior C#/.NET engineers using Cursor. Here's the full week in one read — canonical posts live on [the Agentic Architect blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/).* ## 7 daily senior rules ### Rule 7: IHttpClientFactory Discipline _Sun 14 Jun_ Refuse new HttpClient() in any generated code. Force Cursor to inject IHttpClientFactory or a typed client. The classic socket-exhaustion bug is exactly the kind of footgun an AI hands you without realising. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-14) ### Rule 6: TimeProvider Injection _Sat 13 Jun_ Never let Cursor hardcode DateTime.Now or DateTime.UtcNow in business logic. Inject TimeProvider (or your own IClock) instead. This makes time deterministic for tests and stops the AI reaching for static APIs whenever it generates time-aware code. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-13) ### Rule 5: Minimal API Groups _Fri 12 Jun_ Use MapGroup and EndPoints for .NET 9 services. It keeps the context window lean and focused, helping the AI provide more accurate code suggestions than it can with massive, bloated Controllers. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-12) ### Rule 4: Validator Enforcement _Thu 11 Jun_ Every MediatR Request must have a FluentValidation rule. Force the AI to check the validator before writing handler logic. This prevents "context rot" where the AI forgets your business constraints. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-11) ### Rule 3: Structured Logging _Wed 10 Jun_ Enforce ILogger with structured templates. Never use string interpolation in logs. This ensures that when you feed logs back into Cursor for debugging, the AI recognizes the patterns immediately. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-10) ### Rule 2: Persistence Boundaries _Tue 09 Jun_ Never let the AI write database logic in your Controllers. Enforce a strict boundary where all IQueryable access stays in the Infrastructure layer. This keeps your business logic "pure" and readable for the LLM. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-09) ### Rule 1: The Result Pattern _Mon 08 Jun_ Stop using nulls for flow control. Use a Result object to force Cursor to handle success and failure cases explicitly. This prevents 90% of AI-generated logic errors in Web APIs. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-06-08) --- ## Try one rule before you trust the whole kit The free **[`arch-core-lite.mdc`](https://github.com/agenticstandardcontact-byte/agentic-architect/blob/main/arch-core-lite.mdc?utm_source=devto&utm_medium=weekly_digest&utm_campaign=free_sample)** is one drop-in Cursor rule that ends the morning re-explanation ritual. Install in 60 seconds, see whether Cursor actually remembers your DI lifetimes, and decide for yourself whether the full kit is worth £9.00. - **Free sample:** [`arch-core-lite.mdc` on GitHub](https://github.com/agenticstandardcontact-byte/agentic-architect/blob/main/arch-core-lite.mdc?utm_source=devto&utm_medium=weekly_digest&utm_campaign=free_sample) - **Full kit (£9.00, one-time):** [Agentic Architect Kit](https://payhip.com/b/98aSq?utm_source=devto&utm_medium=weekly_digest&utm_campaign=paid_kit) - **Daily rules feed:** [https://agenticstandardcontact-byte.github.io/agentic-architect/blog/](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/?utm_source=devto&utm_medium=weekly_digest&utm_campaign=blog_index) Canonical home for everything in this digest: [https://agenticstandardcontact-byte.github.io/agentic-architect/blog/](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/).