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

demo地址：https://github.com/PuzzledAlien/log4net_demo/tree/master/DotNetCoreConsole_V2

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;

        /// <summary>

        /// 启动logger

        /// </summary>

        /// <param name="repository">repository名称</param>

        /// <param name="fileName">配置文件名称</param>

        public static void StartLogger(string repository, string fileName)

        {

            _loggerRepository = LogManager.CreateRepository(repository);

            XmlConfigurator.ConfigureAndWatch(_loggerRepository, new FileInfo(fileName));

        }

        /// <summary>

        /// 启动logger

        /// </summary>

        public static void StartLogger()

        {

            _loggerRepository = LogManager.CreateRepository(nameof(MyLogManager));

            XmlConfigurator.ConfigureAndWatch(_loggerRepository, new FileInfo("log4net.config"));

        }

        public static ILog GetMyLog<T>(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 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();

        }