一、log4net简单实例创建步骤如下
1、第一步：在项目中添加对log4net.dll的引用，这里引用版本是2.0.8.0
2、第二步：程序启动时读取log4net的配置文件。
读取log4net的配置文件有两种方式
（1）如果是CS程序，在根目录的Program.cs中的Main方法中添加：log4net.Config.XmlConfigurator.Configure();
如果是BS程序，在根目录的Global.asax.cs（没有新建一个）中的Application_Start方法中添加：log4net.Config.XmlConfigurator.Configure();
（2）无论BS还是CS程序都可直接在项目的AssemblyInfo.cs文件里添加以下的语句：[assembly: log4net.Config .XmlConfigurator()]
3、第三步：在程序使用。
二、具体代码解析
1、建立日志级别枚举
public enum ELogLevel ???{ ???????/// <summary> ???????/// 错误信息 ???????/// </summary> ???????Error = 1, ???????/// <summary> ???????/// 跟踪信息 ???????/// </summary> ???????Trace = 2, ???????/// <summary> ???????/// 调试信息 ???????/// </summary> ???????Debug = 3, ???????/// <summary> ???????/// 记录信息 ???????/// </summary> ???????Info = 4 ???}2、定义ILog接口
public interface ILogger : IDisposable ???{ ???????void LogWithTime(string msg, ELogLevel logLevel = ELogLevel.Error); ???????bool Enabled { get; set; } ???}3、实现ILog接口并且通过代码读取log4net.xml
public class FileLogger : ILogger ???{ ???????private log4net.ILog _log = null; ???????private string _configLogLevel = null; ???????private bool _enabled = true; ???????public FileLogger() ???????{ ???????????this._configLogLevel = GetAppSettingValue("LogLevel"); ???????????string logName = GetAppSettingValue("LogName"); ???????????string configPath = System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "log4net.xml"); ???????????log4net.Config.XmlConfigurator.Configure(new FileInfo(configPath)); ???????????this._log = log4net.LogManager.GetLogger(logName); ???????} ???????/// <summary> ???????/// 获取AppSetting的值 ???????/// </summary> ???????/// <returns></returns> ???????public static string GetAppSettingValue(string key) ???????{ ???????????string value = null; ???????????foreach (string item in System.Configuration.ConfigurationManager.AppSettings) ???????????{ ???????????????if (item.Equals(key, StringComparison.CurrentCultureIgnoreCase)) ???????????????{ ???????????????????value = System.Configuration.ConfigurationManager.AppSettings[key]; ???????????????????break; ???????????????} ???????????} ???????????return value; ???????} ???????#region ILogger成员 ???????public void LogWithTime(string msg, ELogLevel logLevel) ???????{ ???????????if (string.IsNullOrWhiteSpace(msg) || !this._enabled) ???????????{ ???????????????return; ???????????}#if DEBUG ???????????Trace.TraceInformation(msg);#endif ???????????if (string.IsNullOrWhiteSpace(this._configLogLevel)) ???????????{ ???????????????this._configLogLevel = ((int)ELogLevel.Error).ToString(); ???????????} ???????????int configLogLevel = Convert.ToInt32(this._configLogLevel); ???????????if ((int)logLevel <= configLogLevel) ???????????{ ???????????????try ???????????????{ ???????????????????switch (logLevel) ???????????????????{ ???????????????????????case ELogLevel.Error: ???????????????????????????this._log.Error(msg); ???????????????????????????break; ???????????????????????case ELogLevel.Trace: ???????????????????????????this._log.Warn(msg); ???????????????????????????break; ???????????????????????case ELogLevel.Debug: ???????????????????????????this._log.Debug(msg); ???????????????????????????break; ???????????????????????case ELogLevel.Info: ???????????????????????????this._log.Info(msg); ???????????????????????????break; ???????????????????????default: ???????????????????????????break; ???????????????????} ???????????????} ???????????????catch ???????????????{ ???????????????} ???????????} ???????} ???????public bool Enabled ???????{ ???????????get { return this._enabled; } ???????????set { this._enabled = value; } ???????} ???????#endregion ???????#region IDisposable ???????public void Dispose() ???????{ ???????} ???????#endregion ???}4、使用log4net
public partial class Form1 : Form ???{ ???????public Form1() ???????{ ???????????InitializeComponent(); ???????} ???????private void btnLog4net_Click(object sender, EventArgs e) ???????{ ???????????ILogger _fileLogger = new FileLogger(); ???????????_fileLogger.LogWithTime("log4net 日志记录",ELogLevel.Info); ???????????MessageBox.Show("生成的日志地址："+System.AppDomain.CurrentDomain.BaseDirectory); ???????} ???}三、log4net.xml配置
<?xml version="1.0" encoding="utf-8" ?><log4net debug="true"> ?<appender name="FlatFile" type="log4net.Appender.RollingFileAppender,log4net"> ???<param name="File" value="logs/website.log" /> ???<param name="Encoding" value="utf-8" /> ???<param name="AppendToFile" value="true" /> ???<param name="RollingStyle" value="Date" /> ???<param name="ImmediateFlush" value="true" /> ???<param name="MaximumFileSize" value="50MB"/> ???<lockingModel type="log4net.Appender.FileAppender+MinimalLock" /> ???<param name="DatePattern" value="-yyyy.MM.dd‘.log‘" /> ???<param name="StaticLogFileName" value="true" /> ???<layout type="log4net.Layout.PatternLayout,log4net"> ?????<param name="ConversionPattern" value="%-5level [%logger] - %message [%date] %newline" /> ???</layout> ?</appender> ??<root> ???<priority value="DEBUG" /> ???<appender-ref ref="FlatFile" /> ?</root> ?</log4net>
四、注意事项
在Debug模式一切正常，但是在release模式下log4net不工作，查了很多资料，终于解决。具体做如下检查修改。
1、检查log4net写入日志文件路径是否正确；
2、检查对应日志文件路径是否有权限；
3、检查程序log4net配置获取路径；
最常见的问题是第三步，一般都是在AssemblyInfo.cs文件中写入如下代码
[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.xml", ConfigFileExtension = "xml", Watch = true)]
但这个方式在Debug模式下没有问题，但是在release模式下就不好用了，需要在Global.asax文件中具体再次指定配置文件所在位置，例如：
string configPath = System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "log4net.xml"); ???????????log4net.Config.XmlConfigurator.Configure(new FileInfo(configPath));
重新编译发布就可以了。
Log4net学习系列（二）——Log4net的实例
原文地址：https://www.cnblogs.com/qtiger/p/9936824.html