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Changes

Swashbuckle is no longer actively maintained and has been remove from .NET 9 templates. OpenAPI in ASP.NET Core 9 Web API

Log

public class MyClass(ILogger<MyClass> logger)
{
    public void MyMethod()
    {
        // to optimize the performances, test if the log level is enabled
        if (logger.IsEnabled(LogLevel.Debug)) logger.LogDebug("Debug");
        logger.LogTrace("Trace");
        logger.LogInformation("Info");
        logger.LogWarning("Warn");
        logger.LogError("Error");
        logger.LogCritical("Fatal");
    }
}

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",       // log level par défaut
      "Microsoft": "Warning",         // pour les loggers commençant par Microsoft
      "MyNamespace.MyClass": "Debug"  // pour les loggers de MyClass
    }
  }

Program.cs

builder.Logging.ClearProviders();  // remove all the providers: no more logs

The Log methods are synchronous.
There is no file log provider.

Built-in logging providers

Console	VS code "DEBUG CONSOLE" tab In the console window when the app is run with dotnet run
Debug	Debug window when debugging in Visual Studio On Linux journal or /var/log/message or /var/log/syslog
EventSource	Event Tracing for Windows (ETW)
EventLog	Windows Event Log
TraceSource	System.Diagnostics.TraceSource libraries and providers ()
Azure App Service	text files in an Azure App Service app's file system and to blob storage in an Azure Storage account

Console

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Error"  // default log level
    }
  },
  "Console": {
    "LogLevel": {
      "Default": "Information"  // overwrite log level
    },
    "FormatterName": "json"  // log in JSON format
  }
}

journal

mar 19 17:53:10 hostname logtest[29321]: fail: LogTest.Controllers.ItemController[0]
mar 19 17:53:10 hostname logtest[29321]:       Log message

mar 19 17:58:27 hostname logtest[29321]: fail: Microsoft.AspNetCore.Server.Kestrel[13]
mar 19 17:58:27 hostname logtest[29321]:       Connection id "...", Request id "...": An unhandled exception was thrown by the application.
mar 19 17:58:27 hostname logtest[29321]: System.Exception: exception message
mar 19 17:58:27 hostname logtest[29321]:    at LogTest.Controllers.ItemController.ThrowException() in /dev-path/LogTest/Controllers/ItemController.cs:line 41

apache log

access.log is well filled by each query
error.log is never filled