实现目标：将log4net的相关操作封装成一个 .Net Standard类库

demo地址：

Step 1 建立解决方案和处理项目相关配置

在当前解决方案下新建项目，选择 .Net Standard类库，命名“MyLogManager”

nuget引用log4net，添加log4net.config配置，右键点击log4net.config，选择“属性”，修改log4net.config文件属性

刚添加的log4net.config文件属性可能如下图所示（生成操作为无，不复制到输出目录）

需要修改成如下所示（生成操作 无 改为 内容 ，复制到输出目录 - 选择 如果较新则复制）

重新生成解决方案后，在生成目录中就能看到log4net.config文件

Step 2 上代码

思路：两个StartLogger方法，在程序启动时启动该方法，一个方法自己配置处理，一个走默认

代码如下

public class MyLogManager    {        private static ILoggerRepository _loggerRepository;        /// 
        /// 启动logger        /// 
        /// repository名称        /// 配置文件名称        public static void StartLogger(string repository, string fileName)        {            _loggerRepository = LogManager.CreateRepository(repository);            XmlConfigurator.ConfigureAndWatch(_loggerRepository, new FileInfo(fileName));        }        /// 
        /// 启动logger        /// 
        public static void StartLogger()        {            _loggerRepository = LogManager.CreateRepository(nameof(MyLogManager));            XmlConfigurator.ConfigureAndWatch(_loggerRepository, new FileInfo("log4net.config"));        }        public static ILog GetMyLog
    
     (T t)        {            return LogManager.GetLogger(_loggerRepository.Name, t.GetType());        }        public static ILog GetMyLog(object obj)        {            return LogManager.GetLogger(_loggerRepository.Name, obj.GetType());        }        public static ILog GetMyLog(Type type)        {            return LogManager.GetLogger(_loggerRepository.Name, type);        }    }
    

封装之后，调用代码会比第一版本的稍微精简

static void TestV1()        {            MyLogManager.MyLogManager.StartLogger("DotNetCoreConsole_V2", "log4net.config");            var log = MyLogManager.MyLogManager.GetMyLog(typeof(Program));            const int numberOfCycles = 20000;            var sw = Stopwatch.StartNew();            for (var i = 0; i < numberOfCycles; i++)            {                log.InfoFormat("testNum: {0} ", i);            }            sw.Stop();            Console.WriteLine();            Console.WriteLine("Ellapsed: {0}, numPerSec: {1}", sw.ElapsedMilliseconds, numberOfCycles / (sw.ElapsedMilliseconds / (double)1000));            Console.ReadKey();        }

代码重构和优化

思考：可不可以去掉StartLogger这行代码呢？可以。

实现如下

public class NullLogManager    {        private static ILoggerRepository _loggerRepository;        private static ILoggerRepository LoggerRepository        {            get            {                if (_loggerRepository != null)                {                    return _loggerRepository;                }                _loggerRepository = LogManager.CreateRepository(nameof(NullLogManager));                XmlConfigurator.ConfigureAndWatch(_loggerRepository, new FileInfo("log4net.config"));                return _loggerRepository;            }        }        public static ILog GetMyLog
    
     (T t)        {            return LogManager.GetLogger(LoggerRepository.Name, t.GetType());        }        public static ILog GetMyLog(object obj)        {            return LogManager.GetLogger(LoggerRepository.Name, obj.GetType());        }        public static ILog GetMyLog(Type type)        {            return LogManager.GetLogger(LoggerRepository.Name, type);        }        public static ILog GetMyLog()        {            return LogManager.GetLogger(LoggerRepository.Name, nameof(GetMyLog));        }    }
    

调用代码可再次精简

static void TestNullLogManager()        {            var log = MyLogManager.NullLogManager.GetMyLog(typeof(Program));            const int numberOfCycles = 20000;            var sw = Stopwatch.StartNew();            for (var i = 0; i < numberOfCycles; i++)            {                log.InfoFormat("testNum: {0} ", i);            }            sw.Stop();            Console.WriteLine();            Console.WriteLine("Ellapsed: {0}, numPerSec: {1}", sw.ElapsedMilliseconds, numberOfCycles / (sw.ElapsedMilliseconds / (double)1000));            Console.ReadKey();        }