# This week in Cursor + .NET — 7 rules (week ending August 23, 2026)

> Source: <https://dev.to/agentic_architect/this-week-in-cursor-net-7-rules-week-ending-august-23-2026-40ng>
> Published: 2026-08-23 10:41:38+00:00

*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.*

*Sun 23 Aug*

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.

*Sat 22 Aug*

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.

*Fri 21 Aug*

Logs alone won't debug a distributed system. Add a static readonly ActivitySource per project and wrap every external call (DB, HTTP, queue) in StartActivity. Cursor never adds OTEL spans on its own — give it a rule that recognises external-call patterns and proposes the trace.

*Thu 20 Aug*

ValueTask is a perf optimisation for hot paths that often return synchronously. It is not a drop-in for Task. Cursor swaps them around without thinking. Flag ValueTask returns and ask whether the method is actually mostly synchronous. If not, revert to Task.

*Wed 19 Aug*

SendEmail(string to, bool isHtml) should be SendHtmlEmail and SendPlainEmail. Bool flags hide branching that belongs in the type system. Flag any method signature with two or more bool parameters as a refactor candidate.

*Tue 18 Aug*

Long-running work in ASP.NET Core goes in a BackgroundService, not Task.Run inside a controller. Cursor will happily fire Task.Run and call it "async work" — your request thread will die mid-execution and you'll never know why. Catch Task.Run outside test code and propose a hosted service.

*Mon 17 Aug*

System.Threading.Channels beats BlockingCollection and beats roll-your-own queue plus SemaphoreSlim. The AI reaches for ConcurrentQueue every time and stitches it together by hand. A rule that detects producer/consumer patterns and proposes Channel will save you a class.

The free 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.

`arch-core-lite.mdc`

`arch-core-lite.mdc`

on GitHubCanonical home for everything in this digest: [https://agentic-architect.dev/blog/](https://agentic-architect.dev/blog/).