Error handling and logging best practices — Clean Code, Testing & Best Practices

4. Error handling and logging best practices

Intermediate★ Must knowLesson 4 of 12

Throw exceptions for exceptional situations; use TryX or a Result type for expected failures (validation, not found).
Catch only what you can handle; let the rest bubble to a global exception handler (ASP.NET Core UseExceptionHandler + IExceptionHandler / ProblemDetails).
Never swallow exceptions (catch { }).
Structured logging with message templates, not string interpolation:

csharp

// ❌ logger.LogInformation($"Order {orderId} placed by {userId}");   // allocates always; loses structure
// ✅
logger.LogInformation("Order {OrderId} placed by {UserId}", orderId, userId);

// High-performance, source-generated:
public static partial class Log
{
    [LoggerMessage(Level = LogLevel.Warning, Message = "Payment {PaymentId} failed: {Reason}")]
    public static partial void PaymentFailed(ILogger logger, string paymentId, string reason);
}

Never log secrets, passwords, tokens or full card numbers; mask PII.
Use correlation IDs / OpenTelemetry trace IDs to follow a request across services.