DotNet Core Console 程序使用NLog

参考：https://github.com/NLog/NLog/wiki/Tutorial

步骤：

1. 使用Nuget安装NLog.Extensions.Logging

Install-Package NLog.Extensions.Logging

2.编写代码（到这步运行代码，不报错，但是也不会有log输出，因为没有设置配置文件）

3. 编写配置文件

在项目下新增加NLog.config 文件，并设置其能copy到运行目录。将一下内容粘到里面，重新运行程序就可以看到输出到file.txt的log.

    <?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">

      <targets>

        <target name="logfile" xsi:type="File" fileName="file.txt" />

      </targets>

      <rules>

        <logger name="*" minlevel="Info" writeTo="logfile" />

      </rules>

</nlog>

4. 增加输出源，将Log输出到屏幕上,按照以下内容对配置文件做修改

    <?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">

      <targets>

        <target name="logfile" xsi:type="File" fileName="file.txt" />

        <target name="console" xsi:type="Console" />

      </targets>

      <rules>

        <logger name="*" minlevel="Info" writeTo="logfile" />

        <logger name="*" minlevel="Info" writeTo="console" />

      </rules>

</nlog>

5. 如果想发送邮件，可以安装NLog.MailKit

Install-Package NLog.MailKit

6.在配置文件中添加发送邮件的设置部分（参考https://github.com/nlog/NLog/wiki/Mail-target）

    <?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"

          internalLogFile="d:\Nlog_log.txt" internalLogLevel="Error">

      <variable name="smtpServer" value="***"/>

      <variable name="smtpUserName" value="***"/>

      <variable name="smtpPassword" value="***"/>

      <variable name="from" value="***"/>

      <variable name="to" value="***"/>

      <targets>

        <target name="logfile" xsi:type="File" fileName="logs\${date:format=yyyyMMdd}_log.txt" layout="${date:format=yyyy-MM-dd HH\:mm\:ss} ${message}" />

        <target name="console" xsi:type="Console" layout="${date:format=yyyy-MM-dd HH\:mm\:ss} [${level}] ${message}"/>

        <target name="infoMail" xsi:type="Mail"

                  smtpServer="${smtpServer}"

                  smtpUserName="${smtpUserName}"

                  smtpPassword="${smtpPassword}"

                  from="${from}"

                  to="${to}"

                  subject="info log"

                  body="${message}"

                  html="true"/>

        <target name="errorMail" xsi:type="Mail"

                  smtpServer="${smtpServer}"

                  smtpUserName="${smtpUserName}"

                  smtpPassword="${smtpPassword}"

                  from="${from}"

                  to="${to}"

                  subject="error log"

                  body="${message}"/>

      </targets>

      <rules>

        <logger name="***" minlevel="Info" writeTo="infoMail" />

        <logger name="***" minlevel="Error" writeTo="logfile" />

        <logger name="Main" minlevel="Info" writeTo="console" />

        <logger name="Main" minlevel="Error" writeTo="errorMail" />

      </rules>

      <extensions>

        <add assembly="NLog.MailKit"/>

      </extensions>

</nlog>