.net core3.1 使用log4日志

1.NuGet包：

　　log4net.AspNetCore

　　Microsoft.Extensions.Logging.Log4Net.AspNetCore

添加配置文件 log4net.config

　　

<?xml version="1.0" encoding="utf-8"?>
<log4net>
    <!-- Define some output appenders -->
    <appender name="rollingAppender" type="log4net.Appender.RollingFileAppender">
        <file value="loglog.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="INFO" />
            <param name="LevelMax" value="FATAL" />
        </filter>

        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date [%thread] %-5level %logger - %message%newline"/>
        </layout>
    </appender>

    <!-- levels: OFF > FATAL > ERROR > WARN > INFO > DEBUG  > ALL -->
    <root>
        <priority value="ALL"/>
        <level value="ALL"/>
        <appender-ref ref="rollingAppender" />
    </root>
</log4net>

2.配置 CreateHostBuilder

public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args).
                ConfigureLogging(loggingBuilder =>
                {
                    //loggingBuilder.AddFilter("System", LogLevel.Warning);   //过滤系统日志
                    //loggingBuilder.AddFilter("Microsoft", LogLevel.Warning);
                    loggingBuilder.AddLog4Net();//需要配置文件
                })
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });

3.使用

public class FirstController : Controller
    {
        private readonly ILogger<FirstController> _logger;

        public FirstController(ILogger<FirstController> logger)
        {
            _logger = logger;
        }
        public IActionResult Index()
        {
            Console.WriteLine("测试日志");
            _logger.LogWarning("测试日志");
            return View();
        }
    }