How .NET Core Handles Logging and Monitoring

In ASP.NET Core / .NET Core, logging is built-in using the Microsoft.Extensions.Logging framework.

This allows you to log application behavior, errors, performance, and debugging information.

✅ Why Logging is Important

Logging helps you:

✅ Debug issues
✅ Track errors
✅ Monitor performance
✅ Audit user actions
✅ Production troubleshooting

✅ Built-in Logging Providers in .NET Core

.NET Core supports multiple logging providers:

Provider	Purpose
Console	Development logging
Debug	Visual Studio debugging
EventSource	Windows event logs
Azure App Service	Cloud logging

Example built-in providers:

builder.Logging.AddConsole();
builder.Logging.AddDebug();

✅ How to Use Logging in .NET Core

Step 1: Inject ILogger

public class UserService
{
    private readonly ILogger<UserService> _logger;

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

---

✅ Logging Example

_logger.LogInformation("User created successfully");
_logger.LogWarning("User not found");
_logger.LogError("Something went wrong");

✅ Logging Levels

Level	When to Use
Trace	Detailed debugging
Debug	Debugging
Information	Normal flow
Warning	Unexpected situation
Error	Errors
Critical	System crash

Example:

_logger.LogInformation("Application started");
_logger.LogWarning("Memory usage high");
_logger.LogError("Database connection failed");

✅ Logging in Controller Example

[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
    private readonly ILogger<UsersController> _logger;

    public UsersController(ILogger<UsersController> logger)
    {
        _logger = logger;
    }

    [HttpGet]
    public IActionResult Get()
    {
        _logger.LogInformation("Getting users");

        return Ok();
    }
}

✅ Configure Logging in appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "System": "Warning"
    }
  }
}

✅ Production Logging Tools (Real World)

Most companies use:

• Serilog

• NLog

• log4net

Example Using Serilog (Most Popular)

Install packages:

Serilog.AspNetCore
Serilog.Sinks.File

Program.cs:

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("logs/log.txt")
    .CreateLogger();

builder.Host.UseSerilog();

Monitoring in .NET Core

Monitoring tools help track:

• Performance

• Requests

• Failures

• Dependencies

Popular Monitoring Tools:

• Application Insights

• Prometheus

• Grafana

Example Using Application Insights

Install:

Microsoft.ApplicationInsights.AspNetCore

Program.cs:

builder.Services.AddApplicationInsightsTelemetry();

Automatically tracks:

✅ Requests
✅ Exceptions
✅ Dependencies
✅ Performance

Interview Best Answer

If interviewer asks:

How does .NET Core handle logging?

You can answer:

".NET Core uses Microsoft.Extensions.Logging for built-in logging.
We inject ILogger into classes and log messages using different levels like Information, Warning, and Error.
For production, we use tools like Serilog and Application Insights."

Real-World Best Practice

✔ Use ILogger everywhere
✔ Log meaningful messages
✔ Use structured logging
✔ Use external monitoring tools
✔ Log exceptions globally

Example Best Practice

try
{
    // code
}
catch(Exception ex)
{
    _logger.LogError(ex, "Error occurred while processing request");
}

Summary

Feature	.NET Core
Built-in logging	Yes
Multiple providers	Yes
Log levels	Yes
External tools	Yes
Monitoring support	Yes