<?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" >
  <targets>
    <target xsi:type="File" name="f" fileName="${basedir}/logs/${shortdate}.log"
            layout="${longdate} ${uppercase:${level}} ${message}" />
  </targets>
  <rules>
    <logger name="*" minlevel="Trace" writeTo="f" />
  </rules>
</nlog>

    public class NLogTestLib 
    {
        public void Initialize()
        {
            Logger.Trace("logger.Trace");
            Logger.Debug("logger.Debug");
            Logger.Info("logger.Info");
            Logger.Warn("logger.Warn");
            Logger.Error("logger.Error");
            Logger.Fatal("logger.Fatal");
        }
        private Logger Logger
        {
            get
            {
                return LogManager.GetCurrentClassLogger();
            }
        }
    }

        private void TestRun_Click(object sender, EventArgs e)
        {
            NLogTestLib NLogTest = new NLogTestLib();
            NLogTest.Initialize();
            MessageBox.Show("Конец!");
        }