asp.net core3.1 实战开发（log4日志的使用）

首先下nuget下载如下两个包

1. Microsoft.Extensions.Logging.Debug
2. Microsoft.Extensions.Logging.Log4.AspNetCore

在根目录下新建log4net.Config

<?xml version="1.0" encoding="utf-8"?>
<log4net>
	<!-- Define some output appenders -->
	<appender name="rollingAppender" type="log4net.Appender.RollingFileAppender">
		<file value="log\log.txt" />
		<!--追加日志内容-->
		<appendToFile value="true" />

		<!--防止多线程时不能写Log,官方说线程非安全-->
		<lockingModel type="log4net.Appender.FileAppender+MinimalLock" />

		<!--可以为:Once|Size|Date|Composite-->
		<!--Composite为Size和Date的组合-->
		<rollingStyle value="Composite" />

		<!--当备份文件时,为文件名加的后缀-->
		<datePattern value="yyyyMMdd.TXT" />

		<!--日志最大个数,都是最新的-->
		<!--rollingStyle节点为Size时,只能有value个日志-->
		<!--rollingStyle节点为Composite时,每天有value个日志-->
		<maxSizeRollBackups value="20" />

		<!--可用的单位:KB|MB|GB-->
		<maximumFileSize value="3MB" />

		<!--置为true,当前最新日志文件名永远为file节中的名字-->
		<staticLogFileName value="true" />

		<!--输出级别在INFO和ERROR之间的日志-->
		<filter type="log4net.Filter.LevelRangeFilter">
			<param name="LevelMin" value="ALL" />
			<param name="LevelMax" value="FATAL" />
		</filter>
		<layout type="log4net.Layout.PatternLayout">
			<conversionPattern value="%date [%thread] %-5level %logger - %message%newline"/>
		</layout>
	</appender>
	<root>
		<priority value="ALL"/>
		<level value="ALL"/>
		<appender-ref ref="rollingAppender" />
	</root>
</log4net>

配置方式一：program

public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureLogging(loggingBuilder =>
{
   loggingBuilder.AddLog4Net();//需要配置文件
})
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();//靠Startup来串起来MVC
});

配置方式二：Startup

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILoggerFactory loggerFactory)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            loggerFactory.AddLog4Net();

            app.UseSession();

            app.UseHttpsRedirection();
            app.UseStaticFiles(new StaticFileOptions()
            {
                FileProvider = new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot"))
            });

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }

使用方式

public class FirstController : Controller
    {
        private readonly ILogger<FirstController> _logger;
        private readonly ILoggerFactory _loggerFactory;
        public FirstController(ILogger<FirstController> logger,
            ILoggerFactory loggerFactory)
        {
            _logger = logger;
            this._loggerFactory = loggerFactory;
        }

        public IActionResult Index()
        {
            this._logger.LogWarning("日志1");
            this._loggerFactory.CreateLogger<FirstController>().LogWarning("日志2");
            return View();
        }
    }