使用log4net大致分以下几步：
1.安装 log4net，通过 Nuget 下载（或者有log4net.dll的话，直接引用即可）

2.新建 log4net.config 配置文件

<?xml version="1.0" encoding="utf-8" ?>
<configuration><configSections><section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/></configSections><log4net><root></root><appender name="InfoAppender" type="log4net.Appender.RollingFileAppender,log4net" ><param name="File" type="" value="Log/Error/" /><param name="AppendToFile" value="true" /><param name="RollingStyle" value="Date" /><param name="DatePattern" value="yyyyMMdd&quot;.ini&quot;" /><param name="StaticLogFileName" value="false" /><layout type="log4net.Layout.PatternLayout,log4net"><param name="ConversionPattern" value="[%d]%n%m%n" /></layout></appender><appender name="AdoNetAppender" type="log4net.Appender.AdoNetAppender"><bufferSize value="0" /><connectionType value="System.Data.SQLite.SQLiteConnection,System.Data.SQLite" /><connectionString value="Data Source=DataBase\\Log4NetSQLite.db;Version=3;" /><commandText value="INSERT INTO Log (Date, Level, Logger, Message) VALUES (@Date, @Level, @Logger, @Message)" /><parameter><parameterName value="@Date" /><dbType value="DateTime" /><layout type="log4net.Layout.RawTimeStampLayout" /></parameter><parameter><parameterName value="@Level" /><dbType value="String" /><layout type="log4net.Layout.PatternLayout"><conversionPattern value="%level" /></layout></parameter><parameter><parameterName value="@Logger" /><dbType value="String" /><layout type="log4net.Layout.PatternLayout"><conversionPattern value="%logger" /></layout></parameter><parameter><parameterName value="@Message" /><dbType value="String" /><layout type="log4net.Layout.PatternLayout"><conversionPattern value="%message" /></layout></parameter></appender><logger name="Error"><level value="ERROR" /><appender-ref ref="InfoAppender" /></logger><logger name="Info"><level value="INFO" /><appender-ref ref="AdoNetAppender" /></logger></log4net>
</configuration>

3.设置 log4net.config 属性 “复制到输出目录”，选择“始终复制”

4.在 AssemblyInfo.cs 中添加一行代码

[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config", ConfigFileExtension = "config", Watch = true)]

5.写一个通用类 LogHelper

 public class LogHelper{/// <summary>/// 普通日志/// </summary>/// <param name="message">日志内容</param>public static void Info(string message){ILog log = LogManager.GetLogger("Info");if (log.IsInfoEnabled){log.Info(message);}           }/// <summary>/// 错误日志带异常/// </summary>/// <param name="message">错误日志</param>public static void Error(string message, Exception ex){ILog log = LogManager.GetLogger("Error");if (log.IsErrorEnabled){log.Error(message, ex);}}/// <summary>/// 错误日志不带异常/// </summary>/// <param name="message">错误日志</param>public static void Error(string message){ILog log = LogManager.GetLogger("Error");if (log.IsErrorEnabled){log.Error(message);}}}

6.主程序如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp1
{class Program{static void Main(string[] args){string msg = "Star";//LogHelper.Info(msg);//无法向数据库SQLite添加信息LogHelper.Error(msg, new Exception("这是一条异常错误信息"));Console.WriteLine(msg);Console.ReadLine();}}
}

代码整体结构如下：