This week in Cursor + .NET — 6 rules + 3 essays (week ending May 31, 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/).* ## New essays this week ### [How to stop Cursor AI forgetting your .NET architecture (the $9 fix)](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/06-stop-cursor-ai-drift-dotnet.html) _Sat 30 May · .NET tooling_ Cursor forgets your DI patterns, boundaries, and conventions every session. Here's a 4-rule framework that locks your architecture into the AI's long-term memory. ### [How to use Cursor AI with Entity Framework Core (without blowing up your database)](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/07-cursor-efcore-patterns.html) _Sat 30 May · .NET tooling_ Cursor AI generates N+1 queries, eager-loads entire databases, and skips AsNoTracking. Here's a rule-based guardrail system that catches 90% of EF Core mistakes before production. ### [Cursor vs JetBrains Rider for C#/.NET in 2026: which to pay for](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/05-cursor-vs-rider-dotnet.html) _Tue 26 May · .NET tooling_ Senior .NET teams aren't picking - they're paying for both. The honest comparison, the pricing math, and the config that lets the two tools share state. ## 6 daily senior rules ### Rule 18: WebApplicationFactory for Integration Tests _Sun 31 May_ In-memory EF Core providers lie. Use WebApplicationFactory with Testcontainers (SQL Server, Postgres) for real integration coverage. Cursor defaults to UseInMemoryDatabase — it passes locally and ships the bug to production. Flag the in-memory provider in test projects. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-05-31) ### Rule 17: ConfigureAwait false in Libraries _Sat 30 May_ Library code (non-ASP.NET) should ConfigureAwait false on every awaited Task. ASP.NET Core code should not. Cursor mixes the two contexts in the same solution. Detect the project type and enforce the right default. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-05-30) ### Rule 16: async void Outside Event Handlers _Fri 29 May_ async void is a deadlock and unhandled-exception trap everywhere except UI event handlers. The AI uses it routinely for "fire and forget" — wrong answer every time. Flag it on sight. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-05-29) ### Rule 15: Records for Value Objects, Classes for Entities _Thu 28 May_ Value objects (Money, Address, Coordinates) should be records. Entities with identity (Order, Customer) should be classes with an Id. Cursor mixes these constantly. A rule that classifies based on the presence or absence of an identity property keeps the distinction honest. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-05-28) ### Rule 14: Sealed By Default _Wed 27 May_ Mark every class sealed unless inheritance is explicitly planned. Stops Cursor inventing accidental inheritance hierarchies "for flexibility." Small but measurable virtual-call perf wins too. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-05-27) ### Rule 12: IOptionsSnapshot Over Raw Config _Mon 25 May_ Business code should never call IConfiguration directly. Strongly-typed IOptions or IOptionsSnapshot bindings only. The AI loves to "just grab the config value" — refuse it and force a settings class with validation attributes. [→ Permalink on the blog](https://agenticstandardcontact-byte.github.io/agentic-architect/blog/#2026-05-25) --- ## 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 £19.99. - **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 (£19.99, one-time):** [Agentic Architect on Gumroad](https://agenticarchitect.gumroad.com/l/dotnet-persistence-kit?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/).