How do you use logging in ASP.NET Core?
💡 Concept: Logging in ASP.NET Core
Logging is the process of recording application behavior and events for diagnostics and monitoring.
📘 Quick Intro
ASP.NET Core provides a flexible logging framework with built-in support for multiple providers.
🧠 Analogy
Logging is like a black box on an airplane that records every event to help troubleshoot issues.
🔧 Technical Explanation
- ILogger interface is used to write logs in ASP.NET Core.
- Supports built-in providers like Console, Debug, EventSource, EventLog, Azure, etc.
- Log levels include Trace, Debug, Information, Warning, Error, Critical.
- Supports structured logging and scopes.
- Configurable via appsettings.json or code.
🎯 Use Cases
- ✅ Tracking application flow and errors.
- ✅ Performance monitoring.
- ✅ Auditing user activities.
- ✅ Debugging during development and production.
💻 Code Example
// Injecting ILogger in a controller
public class HomeController : Controller {
private readonly ILogger _logger;
public HomeController(ILogger logger) {
_logger = logger;
}
public IActionResult Index() {
_logger.LogInformation(""Index action called."");
return View();
}
}
❓ Interview Q&A
Q1: What is logging?
A: Recording application events for monitoring.
Q2: What interface is used for logging?
A: ILogger.
Q3: Name some built-in logging providers.
A: Console, Debug, EventLog.
Q4: What are log levels?
A: Trace, Debug, Info, Warning, Error, Critical.
Q5: Can logging be configured?
A: Yes, via appsettings.json or code.
Q6: What is structured logging?
A: Logging with named parameters for better querying.
Q7: Is logging important in production?
A: Yes.
Q8: Can logging affect performance?
A: Yes, if not configured properly.
Q9: How to inject logger?
A: Via constructor injection.
Q10: What is logging scope?
A: Contextual information attached to logs.
📝 MCQs
Q1. What interface is used for logging?
- ILogger
- ILog
- ILogging
- Logger
Q2. Name a built-in logging provider.
- File
- Console
- Database
- Event
Q3. What are log levels?
- High, Medium, Low
- Trace, Debug, Info
- Trace, Debug, Information, Warning, Error, Critical
- Error, Warning, Info
Q4. How is logging configured?
- Web.config
- appsettings.json or code
- Environment variables
- Database
Q5. What is structured logging?
- Plain text logging
- Logging with named parameters
- Logging to files
- Event logging
Q6. Is logging important in production?
- No
- Yes
- Maybe
- Sometimes
Q7. How to inject logger?
- Property injection
- Constructor injection
- Method injection
- Manual creation
Q8. What is logging scope?
- Error details
- Contextual information
- User details
- Process info
Q9. Can logging affect performance?
- No
- Yes
- Maybe
- Rarely
Q10. What are some logging providers?
- File, Database
- Console, Debug, EventLog
- Azure, AWS
- Custom providers
💡 Bonus Insight
Effective logging is crucial for diagnosing issues and maintaining healthy ASP.NET Core applications.
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