Bits of .NET

📝 Logging = Observability

Logging is essential. ILogger best practices provide effective logging in .NET Core.

📝 Logging Basics

// Basic Logging
public class UserService
{
    private readonly ILogger _logger;

    public UserService(ILogger logger)
    {
        _logger = logger;
    }

    public async Task GetUserAsync(int id)
    {
        _logger.LogInformation("Getting user {UserId}", id);
        
        try
        {
            var user = await _repository.GetUserAsync(id);
            
            if (user == null)
            {
                _logger.LogWarning("User {UserId} not found", id);
                return null;
            }
            
            _logger.LogInformation("User {UserId} found: {UserName}", id, user.Name);
            return user;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error getting user {UserId}", id);
            throw;
        }
    }
}

// Log Levels
_logger.LogTrace("Trace message");
_logger.LogDebug("Debug message");
_logger.LogInformation("Information message");
_logger.LogWarning("Warning message");
_logger.LogError("Error message");
_logger.LogCritical("Critical message");

🎯 Advanced Logging

// Scoped Logging
using (_logger.BeginScope(new { UserId = userId, RequestId = requestId }))
{
    _logger.LogInformation("Processing request");
    // All logs in this scope include UserId and RequestId
}

// Structured Logging
_logger.LogInformation(
    "User {UserId} purchased {ProductName} for {Price:C}",
    user.Id, product.Name, product.Price);

// Performance Logging
var stopwatch = Stopwatch.StartNew();
await ProcessDataAsync();
stopwatch.Stop();
_logger.LogInformation("Processing took {ElapsedMs}ms", stopwatch.ElapsedMilliseconds);

// Conditional Logging
if (_logger.IsEnabled(LogLevel.Debug))
{
    _logger.LogDebug("Detailed debug information");
}

// Factory Pattern
public class LoggerFactoryService
{
    private readonly ILogger _logger;

    public LoggerFactoryService(ILoggerFactory loggerFactory)
    {
        _logger = loggerFactory.CreateLogger();
    }
}

💡 Logging Tips

• Use appropriate log levels
• Log structured data
• Include correlation IDs
• Don’t log sensitive data
• Use scopes for context