首先我们需要在Nuget中安装Nlog和Nlog-Schema。
添加配置文件：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="d:\nlog\nlog-internal.log">

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

  <variable name="logDir" value="${basedir}/nlog"/>
  <variable name="logFileName" value="${date:format=yyyyMMdd}.txt"/>
  <variable name="logArchiveFileName" value="${date:format=yyyyMMdd}_{#}.txt"/>
  <variable name="logLayout" value="${date:format=yyyy-MM-dd HH\:mm\:ss.fff} [${level}] ${message}"/>

  <!--
  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}" />
    -->

    <target xsi:type="File" name="info"
            layout="${logLayout}"
            fileName="${logDir}/info/${logFileName}"
            archiveFileName="${logDir}/info/${logArchiveFileName}"
            archiveAboveSize="10485760"
            archiveNumbering="Sequence"
            maxArchiveFiles="100"
            concurrentWrites="true"
            keepFileOpen="true"
            openFileCacheTimeout="30"
            encoding="UTF-8" />

    <target xsi:type="File" name="debug"
            layout="${logLayout}"
            fileName="${logDir}/debug/${logFileName}"
            archiveFileName="${logDir}/debug/${logArchiveFileName}"
            archiveAboveSize="10485760"
            archiveNumbering="Sequence"
            maxArchiveFiles="100"
            concurrentWrites="true"
            keepFileOpen="true"
            openFileCacheTimeout="30"
            encoding="UTF-8" />

    <target xsi:type="File" name="error"
            layout="${logLayout}"
            fileName="${logDir}/error/${logFileName}"
            archiveFileName="${logDir}/error/${logArchiveFileName}"
            archiveAboveSize="10485760"
            archiveNumbering="Sequence"
            maxArchiveFiles="100"
            concurrentWrites="true"
            keepFileOpen="true"
            openFileCacheTimeout="30"
            encoding="UTF-8" />

    <target xsi:type="File" name="warn"
        layout="${logLayout}"
        fileName="${logDir}/warn/${logFileName}"
        archiveFileName="${logDir}/warn/${logArchiveFileName}"
        archiveAboveSize="10485760"
        archiveNumbering="Sequence"
        maxArchiveFiles="100"
        concurrentWrites="true"
        keepFileOpen="true"
        openFileCacheTimeout="30"
        encoding="UTF-8" />

  </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" />
    -->

    <logger name="*" minlevel="Info" maxlevel="Info" writeTo="info" />

    <logger name="*" minlevel="Debug" maxlevel="Debug" writeTo="debug" />

    <logger name="*" minlevel="Error" maxlevel="Error" writeTo="error" />

    <logger name="*" minlevel="Warn" maxlevel="Warn" writeTo="warn" />

  </rules>
</nlog>

定义了5种log类型Debug，Info，Debug，Error，Warn，详细配置可以自己定义。
定义一个常用的log类

  public class NLogHelper
  {
      private static Logger _log = NLog.LogManager.GetCurrentClassLogger();

      /// <summary>
      /// Debug日志
      /// </summary>
      /// <param name="log"></param>
      public static void Debug(string log)
      {
          _log.Debug(log);
      }

      /// <summary>
      /// Error日志
      /// </summary>
      /// <param name="log"></param>
      public static void Error(string log)
      {
          _log.Error(log);
      }

      /// <summary>
      /// Warn日志
      /// </summary>
      /// <param name="log"></param>
      public static void Warn(string log)
      {
          _log.Warn(log);
      }

      /// <summary>
      /// Info日志
      /// </summary>
      /// <param name="log"></param>
      public static void Info(string log)
      {
          _log.Info(log);
      }

      /// <summary>
      /// 详细异常日志
      /// </summary>
      /// <param name="ex"></param>
      public static void Exception_Error(Exception ex)
      {
          try
          {
              if (ex != null)
              {
                  StringBuilder strBuilder = new StringBuilder();
                  strBuilder.Append("【异常日志消息】");
                  strBuilder.AppendLine(ex.Message);
                  strBuilder.Append("【异常日志Trace】");
                  strBuilder.AppendLine(ex.StackTrace);
                  strBuilder.Append("【异常日志全部】");
                  strBuilder.Append(ex.ToString());
                  _log.Error(strBuilder.ToString());
              }
          }
          catch (Exception)
          {
          }
      }
  }

调用代码

   NLogHelper.Info($"系统正在运行中...");