1：下載log4net.dll檔案，然後在專案中新增引用；
2：新建xml檔案，配置log4，配置資訊如下：

<?xml version="1.0" encoding="utf-8" ?>

<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  </configSections>

  <log4net>
    <root
 
>
      <level value="WARN" />
      <appender-ref ref="LogFileAppender" />
      <appender-ref ref="ConsoleAppender" />
    </root>

    <logger name="testApp.Logging">
      <level value="DEBUG"/>
    </logger>

    <appender name="LogFileAppender" type="log4net.Appender.FileAppender"
 
 >
      <param name="File" value="log\log-file.txt" />
      <param name="AppendToFile" value="true" />

      <layout type="log4net.Layout.PatternLayout">
        <param name="Header" value="[Header]&#13;&#10;"/>
        <param name="Footer" value="[Footer]&#13;&#10;"
 
/>
        <param name="ConversionPattern" value="%d [%t] %-5p %c [%x]  - %m%n" />
      </layout>

      <filter type="log4net.Filter.LevelRangeFilter">
        <param name="LevelMin" value="DEBUG" />
        <param name="LevelMax" value="FATAL" />
      </filter>
    </appender>

    <appender name="ConsoleAppender"  type="log4net.Appender.ConsoleAppender" >
      <layout type="log4net.Layout.PatternLayout">
        <param name="ConversionPattern"  value="%d [%t] %-5p %c [%x] - %m%n" />
      </layout>
      <!--<layout type="log4net.Layout.SimpleLayout"/>-->

    </appender>

  </log4net>
</configuration>

注意：新建的xml檔案必須放在debug目錄下；
3：在Program.cs中初始化log4，資訊如下：

    string assemblyFilePath = Assembly.GetExecutingAssembly().Location;
            string assemblyDirPath = Path.GetDirectoryName(assemblyFilePath);
            string configFilePath = assemblyDirPath + " \\Log4.xml";
            log4net.Config.XmlConfigurator.ConfigureAndWatch(new FileInfo(configFilePath));

            ILog log = LogManager.GetLogger("testApp.Logging");
            Console.WriteLine("日誌記錄開始....");

4：新建winform窗體，新增一個按鈕測試
log4net.ILog log = log4net.LogManager.GetLogger(“testApp.Logging”);//獲取一個日誌記錄器
log.Info(DateTime.Now.ToString() + “:開始點下按鈕…….”);//寫入一條新log
try
{
//記錄錯誤日誌
log.Error(“打算用1除以0：”, new Exception(“在窗體中可能要發生一個異常！”));
int i = 0;
int j = 1;
int s = j / i;
}
catch (Exception ec)
{
//記錄嚴重錯誤
log.Fatal(“在窗體中發生了一個致命錯誤”, ec);
}

        log.Info(DateTime.Now.ToString() + ":按鈕點選完成.......");//寫入一條新log

5：基本完成，開啟debug資料夾，發現多了log資料夾，表示成功！