csharplisted

# 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> { public sealed record Ok(T Value) : Result<T>; public sealed record Fail(string Error) : Result<T>; } var message = GetUser(id) switch { Result<User>.Ok(var user) => $"Fo