csharp

• SKILL.mdcore · 3,958 bytes

# C# Conventions

House conventions for C# 12 / .NET 8+. Apply them to code you are writing or changing — don't rewrite untouched files to match unless asked.

## Conventions

- **`<Nullable>enable</Nullable>` and warnings as errors.** The nullable annotations only pay off if the warnings block the build; ignored, they become decoration that lies about which references can be null.
- **C# 12 defaults:** file-scoped namespaces, primary constructors, collection expressions, `required` members. Records for DTOs and value objects — value equality is what you want when comparing data, and hand-written `Equals`/`GetHashCode` pairs drift apart.
- **Pattern matching over type-test-and-cast chains.** Switch expressions on a closed hierarchy let the compiler warn about unhandled cases; an `if`/`else if` ladder just falls through silently when a new type appears.
- **Result pattern for expected failures**, exceptions for genuinely exceptional ones. "Not found" and "invalid input" are ordinary outcomes and belong in the return type where the caller must deal with them; using exceptions for control flow hides them from the signature and costs a stack unwind per occurrence. A closed record hierarchy gives you exhaustive `switch` over the outcomes:

  ```csharp
  public abstract record Result<T>
  {