[NLog] 日志配置与控件RichTextBox配置

（1）引用NLog和NLog.Windows.Forms

（2）配置app.config文件

<configSections>    
    <section name="nlog" type="NLog.Config.ConfigSectionHandler, NLog" />
  </configSections>

  <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">
    <targets>
      <target name="t1" xsi:type="File" fileName="${basedir}/logs/${shortdate}.log" layout="${longdate} - ${level:uppercase=true} - ${logger} - ${message}  ${exception:format=tostring}" />
      <target xsi:type="RichTextBox"
        name="textbox"
        layout="${longdate} - ${level:uppercase=true} - ${logger} - ${message}  ${exception:format=tostring}"
        autoScroll="true"
        maxLines="100"
        controlName="tbLogShow"
        formName="MainForm"
        useDefaultRowColoringRules="true"/>
    </targets>
    <rules>
      <logger name="*" minlevel="Debug" maxlevel="Error" writeTo="t1" />
      <logger name="*" minlevel="Debug" maxlevel="Error" writeTo="textbox" />
    </rules>
  </nlog>

（3）在确定控件对象生成以后（例如MainForm_Load里），再定义logger

private static ILogger _logger = null;

private void MainForm_Load(object sender, EventArgs e)
{
    if (_logger == null)
       _logger = NLog.LogManager.GetCurrentClassLogger();           
    }
}

ps：不添加NLog.Windows.Forms或未满足条件3，控件RichTextBox将不显示日志