---
applyTo: "**/*.cs"
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# C# Coding Standards

## Language & Target
- All code must be written in C# targeting **.NET 10**.
- The original Fuchs intranet was VB.NET; any remaining VB must be converted to C# during migration. Original VB reference lives at `D:\My Programming\PWProjects\Fuchs\Fuchs\Areas\Intranet`.

## Style
- Follow standard C# naming: **PascalCase** for classes and methods, **camelCase** for locals and parameters, `_camelCase` for private fields.
- `ImplicitUsings` and `Nullable` are enabled in the Fuchs project — honor nullable annotations and avoid redundant `using` directives.
- Prefer modern, performance-oriented features: `async`/`await` for I/O, LINQ for data manipulation, dependency injection for testability, `switch` expressions, target-typed `new`, and collection initializers.
- Only add comments when they match the existing style or explain non-obvious logic. Do not over-comment.

## File Size
- Keep files to a soft limit of **400** lines (hard max **600**).
- Proactively refactor larger files into smaller, focused classes/partials — this is why `IntranetController` is split into domain partials.

## Dependency Injection
- Inject dependencies via constructor (`ILogger<T>`, `IConfiguration`, services). Do not use service-locator or static singletons in new class-level code.
- Library classes accept optional loggers (`ILogger<T>?`) defaulting to `NullLogger<T>.Instance` — see `logging.instructions.md`.

## Packages
- Do not upgrade `Spire.PDF` beyond `8.10.5`.
- For builds failing because `SixLabors.ImageSharp` (v4.0.0+) requires a license, see `imagesharp.instructions.md` before downgrading.
- Keep `MailKit`/`MimeKit` versions aligned with OCORE's referenced versions to avoid `NU1605` package-downgrade-as-error.
- Only add or update packages when necessary; prefer existing/OCORE libraries.