Logging Standards for C# Applications

Comprehensive logging guidelines for consistent, structured, and maintainable logging across C# applications with emphasis on mental wellness platform requirements.

Core Logging Principles

Message Format Pattern

REQUIRED: All log messages MUST follow this pattern:

code

[CLASS_NAME_OR_SERVICE]: MESSAGE

The prefix should be the actual class name or service name where the logging occurs, enclosed in square brackets.

Examples by Log Level

Information Level

csharp

_logger.LogInformation("[SystemNotificationService]: Notification {NotificationId} sent to user {UserId}",
    notificationId, userId);

_logger.LogInformation("[ActivityController.Store]: Activity saved to database - ActivityId: {ActivityId}",
    activity.Id);

_logger.LogInformation("[ContentService]: Retrieved {Count} published meditations for institution {InstitutionId}",
    count, institutionId);

Warning Level

csharp

_logger.LogWarning("[DeviceTokenService]: User {UserId} has no registered device tokens", userId);

_logger.LogWarning("[AnalyticsService]: Failed to queue event - {EventType}: {EventName} for UserId: {UserId}",
    eventType, eventName, userId);

_logger.LogWarning("[BadgeEvaluationService]: Badge definition {BadgeId} not found during evaluation", badgeId);

Error Level

csharp

_logger.LogError(ex, "[BadgeService]: Failed to award badge {BadgeId} to user {UserId}", badgeId, userId);

_logger.LogError(ex, "[NotificationService]: Failed to send notification {NotificationId}", notificationId);

_logger.LogError(ex, "[ActivityController.Store]: Failed to track activity analytics for user {UserId}", userId);

Debug Level

csharp

_logger.LogDebug("[CachedContentService]: Cache hit for content type {ContentType}", contentType);

_logger.LogDebug("[AnalyticsService]: Track event sent - Event: {EventName}, UserId: {UserId}, SessionId: {SessionId}",
    eventName, userId, sessionId);

_logger.LogDebug("[ActivityController.Store]: MapEventToActivityType result - Event: {Event}, ContentType: {ContentType}, MappedActivityType: {ActivityType}",
    activity.Event, activity.ContentType, activityType ?? "NULL");

Structured Logging Best Practices

1. Use Named Parameters

✅ DO THIS - Structured logging with named parameters:

csharp

_logger.LogInformation("[NotificationService]: Notification {NotificationId} sent to user {UserId} at {Timestamp}",
    notificationId, userId, DateTime.UtcNow);

❌ AVOID THIS - String interpolation or concatenation:

csharp

// Bad - loses structured logging benefits
_logger.LogInformation($"[NotificationService]: Notification {notificationId} sent to user {userId}");

2. Include Relevant Entity IDs

Always include key identifiers for troubleshooting:

•UserId
•NotificationId
•ActivityId
•BadgeId
•ContentId
•SessionId
•InstitutionId

csharp

_logger.LogInformation("[BadgeService]: Badge {BadgeId} awarded to user {UserId} - TotalPoints: {Points}",
    badgeId, userId, totalPoints);

3. Exception Logging Format

Always use exception-first format:

csharp

// Correct - exception as first parameter
_logger.LogError(ex, "[ServiceName]: Error message with {ContextParam}", contextValue);

// Incorrect - exception in message
_logger.LogError($"[ServiceName]: Error occurred: {ex.Message}");

Log Levels Guide

Debug

•When: Diagnostic information useful during development
•Examples: Cache hits/misses, method entry/exit, internal state changes
•Audience: Developers debugging specific issues
•Production: Typically disabled in production

csharp

_logger.LogDebug("[UserActivityTrackingService]: Processing activity event - ActivityType: {ActivityType}, EntityId: {EntityId}",
    activityType, entityId);

Information

•When: Normal application flow, significant events
•Examples: Successful operations, user actions, state transitions
•Audience: Operations team, system monitoring
•Production: Enabled, but should not be excessive

csharp

_logger.LogInformation("[AnalyticsService]: Initialized with Segment integration (write key configured)");

Warning

•When: Unexpected but recoverable situations
•Examples: Missing optional data, fallback behavior triggered, performance degradation
•Audience: Operations team for monitoring
•Production: Always enabled

csharp

_logger.LogWarning("[ActivityController.Store]: {ErrorMessage}", errorMessage);

Error

•When: Operation failures, exceptions
•Examples: Database errors, external API failures, validation failures
•Audience: Operations team, on-call engineers
•Production: Always enabled, may trigger alerts

csharp

_logger.LogError(ex, "[AnalyticsService]: Failed to send analytics event {EventName} for user {UserId}",
    eventName, userId);

Critical

•When: Application-threatening failures
•Examples: Database connection lost, critical service unavailable
•Audience: Immediate escalation to on-call
•Production: Always enabled, triggers immediate alerts

csharp

_logger.LogCritical(ex, "[DatabaseService]: Unable to establish database connection after {RetryAttempts} attempts",
    retryAttempts);

Common Patterns by Component Type

Controllers

csharp

_logger.LogInformation("[ActivityController.Store]: Received activity - Event: {Event}, ContentType: {ContentType}, SessionId: {SessionId}",
    data.Event, data.ContentType, data.SessionId);

_logger.LogWarning("[ActivityController.Store]: {ErrorMessage}", errorMessage);

Services

csharp

_logger.LogInformation("[BadgeService]: Evaluating badges for user {UserId} - ActivityType: {ActivityType}",
    userId, activityType);

_logger.LogError(ex, "[NotificationService]: Failed to process notification for user {UserId}", userId);

Background Jobs

csharp

_logger.LogInformation("[NotificationSchedulingJobService]: Starting scheduled notification job");

_logger.LogWarning("[NotificationSchedulingJobService]: No notifications scheduled for processing");

Analytics & Tracking

csharp

_logger.LogDebug("[AnalyticsService]: Added sessionId {SessionId} to Segment context for user {UserId}",
    sessionId, userId);

_logger.LogInformation("[AnalyticsService]: {EventType}: {EventName} - UserId: {UserId}, Properties: {Properties}",
    eventType, eventName, userId, FormatProperties(properties));

Anti-Patterns to Avoid

❌ Don't Use Generic Prefixes

csharp

// Bad - not specific enough
_logger.LogInformation("[Service]: Operation completed");

// Good - identifies exact service
_logger.LogInformation("[BadgeEvaluationService]: Badge evaluation completed for user {UserId}", userId);

❌ Don't Use "SEGMENT" or Technology Names

csharp

// Bad - uses technology name instead of class name
_logger.LogDebug("SEGMENT Track: {eventName}");

// Good - uses actual class name
_logger.LogDebug("[AnalyticsService]: Track event sent - Event: {EventName}", eventName);

❌ Don't Log Sensitive Data

csharp

// Bad - logs sensitive information
_logger.LogInformation("[AuthService]: User logged in - Password: {Password}", password);

// Good - logs only non-sensitive identifiers
_logger.LogInformation("[AuthService]: User {UserId} logged in successfully", userId);

❌ Don't Use String Interpolation in Log Messages

csharp

// Bad - loses structured logging
_logger.LogInformation($"[Service]: User {userId} performed action");

// Good - uses structured logging
_logger.LogInformation("[Service]: User {UserId} performed action", userId);

❌ Don't Log in Tight Loops Without Throttling

csharp

// Bad - can flood logs
foreach (var item in largeCollection)
{
    _logger.LogDebug("[Service]: Processing item {ItemId}", item.Id);
}

// Good - log summary instead
_logger.LogInformation("[Service]: Processing {Count} items", largeCollection.Count);
// Log only errors or specific cases

Log Message Guidelines

Be Specific and Actionable

csharp

// Bad - vague
_logger.LogError("[Service]: Error occurred");

// Good - specific and actionable
_logger.LogError(ex, "[NotificationService]: Failed to send push notification to device {DeviceToken} - User: {UserId}",
    deviceToken, userId);

Use Present Tense for Actions

csharp

// Preferred
_logger.LogInformation("[Service]: Processing request");
_logger.LogInformation("[Service]: Request processed successfully");

// Not preferred
_logger.LogInformation("[Service]: Will process request");

Include Context for Troubleshooting

csharp

_logger.LogWarning("[CachedContentService]: Cache miss for content type {ContentType} - InstitutionId: {InstitutionId}",
    contentType, institutionId);

Performance Considerations

Use LogLevel Checks for Expensive Operations

csharp

if (_logger.IsEnabled(LogLevel.Debug))
{
    var detailedInfo = ExpensiveSerializationMethod(data);
    _logger.LogDebug("[Service]: Detailed state - {DetailedInfo}", detailedInfo);
}

Avoid Logging in Hot Paths

Only log at Information level or higher in performance-critical code. Use Debug level sparingly.

Testing Logging

When writing unit tests, verify logging behavior:

csharp

_mockLogger.Verify(
    x => x.Log(
        LogLevel.Information,
        It.IsAny<EventId>(),
        It.Is<It.IsAnyType>((o, t) => o.ToString().Contains("[BadgeService]")),
        null,
        It.IsAny<Func<It.IsAnyType, Exception, string>>()),
    Times.Once);

Quick Reference

Scenario	Log Level	Include
Successful operation	Information	Entity IDs, key parameters
Operation started	Debug	Context parameters
Unexpected but handled	Warning	What happened, how it was handled
Operation failed	Error	Exception, entity IDs, context
System critical failure	Critical	Exception, impact scope
Development debugging	Debug	Detailed state information

Compliance & Privacy

HIPAA/GDPR Considerations

•NEVER log Protected Health Information (PHI)
•NEVER log personally identifiable information (PII) beyond user IDs
•NEVER log passwords, tokens, or credentials
•Use hashed/anonymized identifiers where appropriate

csharp

// Good - logs hashed user identifier
_logger.LogDebug("[AnalyticsService]: Using hashed user ID for Segment");

// Bad - would log sensitive data
// _logger.LogDebug("[AnalyticsService]: User email: {Email}", userEmail);

Remember: Consistent, structured logging is essential for troubleshooting production issues, monitoring application health, and maintaining a high-quality codebase. Follow these standards religiously to ensure logs are useful and actionable.