nlogGetting started with nlog


Remarks

NLog is a free logging library for .NET. It is licensed under BSD-3, meaning it can be used in commercial applications.

NLog's source can be found at GitHub

Versions

Major versions:

versionrelease notesrelease date
4release notes2015-06-09
3release notes2014-06-02
2release notes2011-07-18
1release notes2011-01-07

Writing first logs

Install the NLog.Config package. (NuGet 3 users should install NLog and add the config manually.) Write to logger:

using NLog;

public class MyClass
{
  private static Logger logger = LogManager.GetCurrentClassLogger();

  public void MyMethod1()
  {
    logger.Trace("Sample trace message");
    logger.Debug("Sample debug message");
    logger.Info("Sample informational message");
    logger.Warn("Sample warning message");
    logger.Error("Sample error message");
    logger.Fatal("Sample fatal error message");

    // alternatively you can call the Log() method 
    // and pass log level as the parameter.
    logger.Log(LogLevel.Info, "Sample informational message");

    try
    {
        SendMail();
    }
    catch(Exception ex)
    {
       //example writing exception
      logger.Error(ex, "Error when sending mail");
    }
  }
}
 

This example config should be added with the NLog.Config package. Otherwise add the following to the root of the application - or next to the .dll as "nlog.config"

<?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} ${exception}" />
   
  </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>
 

The config writes the log messages to a file.