NLog

Creates and manages instances of Logger objects.

Install from nuget: NLog 4.7.0

Configuration

  1. Create NLog.config with default template data
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<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd NLog.xsd"
      autoReload="true"
      throwExceptions="false"
      internalLogLevel="Off" internalLogFile="c:\temp\nlog-internal.log">

  <!-- optional, add some variables
  https://github.com/nlog/NLog/wiki/Configuration-file#variables
  -->
  <variable name="myvar" value="myvalue"/>

  <!--
  See https://github.com/nlog/nlog/wiki/Configuration-file
  for information on customizing logging rules and outputs.
   -->
  <targets>

    <!--
    add your targets here
    See https://github.com/nlog/NLog/wiki/Targets for possible targets.
    See https://github.com/nlog/NLog/wiki/Layout-Renderers for the possible layout renderers.
    -->

    <!--
    Write events to a file with the date in the filename.
    <target xsi:type="File" name="f" fileName="${basedir}/logs/${shortdate}.log"
            layout="${longdate} ${uppercase:${level}} ${message}" />
    -->
  </targets>

  <rules>
    <!-- add your logging rules here -->

    <!--
    Write all events with minimal level of Debug (So Debug, Info, Warn, Error and Fatal, but not Trace)  to "f"
    <logger name="*" minlevel="Debug" writeTo="f" />
    -->
  </rules>
</nlog>

This came from:

  1. Set the file to always copy

Always Copy

  1. Configure the file
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<targets>
    <target name="logfile"
        xsi:type="File" 
        archiveNumbering="Date"
        archiveEvery="Day"
        maxArchiveFiles="50"
        bufferSize="102400"
        fileName="appname.log" />
</targets>

<rules>
    <logger name="*" writeTo="logfile" />
</rules>

Example use

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var logger = NLog.LogManager.GetCurrentClassLogger();

logger.Debug("Some debug");
logger.Debug("Some other debug"); 
logger.Info("Some info.");

~ this will then create `appname.log` in your executing bin directory.

Configure for Dependency Injection

Install from nuget: NLog.Web.AspNetCore 4.9.2

  1. Update Program.cs

BEFORE

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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace GameUI
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>();
    }
}

AFTER

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using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using NLog.Web;
using Microsoft.Extensions.Logging;
using System;

namespace GameUI
{
    public class Program
    {
        public static void Main(string[] args)
        {
            // NLog: setup the logger first to catch all errors
            var logger = NLog.Web.NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();
            try
            {
                logger.Debug("init main");
                CreateWebHostBuilder(args).Build().Run();
            }
            catch (Exception ex)
            {
                //NLog: catch setup errors
                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)
                NLog.LogManager.Shutdown();
            }
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args)
        {
            return WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>()
            .ConfigureLogging(logging =>
            {
                logging.ClearProviders();
                logging.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);
            })
            .UseNLog();  // NLog: setup NLog for Dependency injection
        }
    }
}
  1. Configure appsettings.json

If you are debugging locally make the changes in appsettings.Development.json

The Logging configuration specified in appsettings.json overrides any call to SetMinimumLevel. So either remove "Default": or adjust it correctly to your needs. - github.com/NLog

BEFORE

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{
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  }
}

AFTER

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{
  "Logging": {
    "LogLevel": {
      "Default": "Trace",
      "Microsoft": "Information"
    }
  }
}
  1. Inject into your constructor
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using Microsoft.Extensions.Logging;

public class ComputerMoveHard : IComputerMove
{
    private readonly ILogger<ComputerMoveHard> _logger;

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

    public int SetPosition(...)
    {
        _logger.LogTrace("This is LogTrace");
        _logger.LogDebug("This is LogDebug");
        _logger.LogInformation("This is LogInformation");
        _logger.LogWarning("This is LogWarning");
        _logger.LogError("This is LogError");
        _logger.LogCritical("This is LogCritical");

Log Levels

These levels work from minimum (Trace) to maximum (Critical), so if you set your level to Information you will not get logs for Trace and Debug

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Trace - Very detailed log messages, potentially of a high frequency and volume
Debug - Less detailed and/or less frequent debugging messages
Information - Informational messages
Warning - Warnings which don't appear to the user of the application
Error - Error messages
Critical - Fatal error messages. After a fatal error, the application usually terminates.
None - No logging

Logging To Different Files

You can specify logging to files by class and wildcard, super useful for debugging code flows. For the below I needed only logs for moverules from the name space GameEngine.Services.ComputerMove.MoveRules.*

So for the below I would include _logger.LogTrace("This is LogTrace"); in the code for the MoveRules classes and this data will go into moverules.log

Note that appsettings needs to then be set to Trace.

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<targets>
  <target name="moverules"
      xsi:type="File"
      archiveNumbering="Date"
      archiveEvery="Day"
      maxArchiveFiles="50"
      bufferSize="102400"
      fileName="moverules.log" />
  <target name="tictactoe"
      xsi:type="File"
      archiveNumbering="Date"
      archiveEvery="Day"
      maxArchiveFiles="50"
      bufferSize="102400"
      fileName="tictactoe.log" />
</targets>

<rules>
	<logger name="GameEngine.Services.ComputerMove.MoveRules.*" level="Trace" writeTo="moverules" />
    <logger name="*" minlevel="Debug" writeTo="tictactoe" />
</rules>

References