modern-csharp-coding-standards

Use record types for immutable DTOs and domain entities, and readonly record structs for value objects. Combine them with switch expressions, property patterns, and relational patterns to replace verbose if-else chains with expressive matching logic.

Use record class for entities, aggregates, and DTOs with multiple properties where reference semantics fit. Use readonly record struct for value objects like Money or OrderId, since they get value semantics, stack allocation, and no GC pressure.

Use Span<T> and ReadOnlySpan<T> for synchronous slicing and parsing without allocations, Memory<T> when crossing await boundaries, and ArrayPool<T> for large temporary buffers. Replace substring calls with span slicing to eliminate intermediate string allocations.

Use a Result<T, TError> type for expected errors like validation failures, business rule violations, and not-found cases. Reserve exceptions for unexpected failures such as network errors, system faults, or programming bugs.

Yes, I/O-bound operations should be async end-to-end with CancellationToken parameters defaulted and propagated through the call stack. Never block on async code with .Result, and use ValueTask for frequently-called methods that often complete synchronously.

Inheritance is acceptable mainly for framework requirements like ControllerBase in ASP.NET Core or custom exceptions. Application code should prefer composition with interfaces, static helper classes, and records modeling variants instead of abstract base class hierarchies.