Dernière version du 19 mars 2023 à 13:31

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Getting started

Console project

Nuget packages

NLog.Extensions.Logging
Microsoft.Extensions.DependencyInjection
Microsoft.Extensions.Configuration.Json

Config file

Be sure to have the config file copied to the output folder while building.

appsettings.json

{
  "NLog": {
    "throwConfigExceptions": true,
    "targets": {
      "async": true,
      "console": {
        "type": "ColoredConsole",
        "layout": "${level:uppercase=true} - ${logger} - ${message:withexception=true}"
      }
    },
    "rules": [
      {
        "logger": "*",
        "minLevel": "Info",
        "writeTo": "console"
      }
    ]
  }
}

Program

Program.cs

var logger = LogManager.GetCurrentClassLogger();

try
{
    var config = new ConfigurationBuilder()
       .SetBasePath(Directory.GetCurrentDirectory())
       .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
       .Build();

    // to log in this class only
    LogManager.Configuration = new NLogLoggingConfiguration(config.GetSection("NLog"));

    using var servicesProvider = new ServiceCollection()
        .AddTransient<MyApp>()
        .AddLogging(loggingBuilder =>
        {
            // configure Logging with NLog
            loggingBuilder.ClearProviders();
            loggingBuilder.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);
            loggingBuilder.AddNLog(config);
        }).BuildServiceProvider();

    var myApp = servicesProvider.GetRequiredService<MyApp>();
    myApp.Run();
}
catch (Exception ex)
{
    // NLog: catch any exception and log it.
    logger.Error(ex, "Stopped program because of exception");
    throw;
}
finally
{
    // Ensure to flush and stop internal timers/threads before application-exit (Avoid segmentation fault on Linux)
    LogManager.Shutdown();
}

Configuration file

Layout

// default layout
"layout": "${longdate}|${level:uppercase=true}|${logger}|${message:withexception=true}"

Target

ColoredConsole

appsettings.json

"async": true, // use the asynchronous NLog Console Target
"console": {
  "type": "ColoredConsole",
  "layout": "${level:uppercase=true} - ${logger} - ${message:withexception=true}",
  "useDefaultRowHighlightingRules": false,
  "rowHighlightingRules": [
    {
      "condition": "level == LogLevel.Fatal",
      "foregroundColor": "Blue",
      "backgroundColor": "White"
    }
  ]
}

NLog Console vs AddConsole

File

appsettings.json

"file": {
  "type": "File",
  "fileName": "${basedir}/logs/nlog.log",

  // Global Mutex Locks
  "keepFileOpen": true,
  "concurrentWrites": true,

  // Size-based file archival
  "archiveFileName": "${basedir}/archives/nlog.{#####}.log",
  "archiveAboveSize": 10240,
  "maxArchiveFiles": 4,
  "archiveNumbering": "Rolling"
}

FileTarget Archive Examples

Rules

"rules": [
  {
    "logger": "*",
    "minLevel": "Info",
    "writeTo": "console, file"
  },
  {
    "logger": "*",
    "levels": "Debug",
    "writeTo": "file"
  }
]

Filters

Filters apply the default action except for the matching conditions.

"rules": [
  {
    "logger": "*",
    "minLevel": "Info",
    "writeTo": "console, file",
    "filterDefaultAction": "Log",
    "filters": [
      {
        "type": "when",
        "condition": "contains('${message}','Common')",
        "action": "Ignore"
      }
    ]
  }
]

Levels

Level	Description
FATAL	Fatal error messages. After a fatal error, the application usually terminates
ERROR	Error messages
WARN	Warnings which don't appear to the user of the application
INFO	Informational messages
DEBUG	Less detailed and/or less frequent debugging messages
TRACE	Very detailed log messages, potentially of a high frequency and volume