1. 介绍

NLog是适用于各种.NET平台（包括.NET标准）的灵活，免费的日志记录平台，支持数据库、文件、控制台。

2. 输入到文件

2.1 引用nuget包

    <PackageReference Include="NLog" Version="4.7.6" /><PackageReference Include="NLog.Web.AspNetCore" Version="4.9.3" />

2.2 创建NLog配置文件

在项目目录中新建一个xml文件的nlog.config

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><targets async="true"><target name="file" xsi:type="File"layout="${longdate} ${logger} ${message}${exception:format=ToString}"fileName="${basedir}/logs/${date:format=yyyy-MM-dd}.txt"keepFileOpen="true"encoding="utf-8" /><target name="console" xsi:type="Console"><attribute name="time" layout="${date:format=yyyy-MM-dd HH\:mm\:ss.fff zzz}" /><attribute name="category" layout="${logger}" /><attribute name="log_level" layout="${level:lowerCase=true}" /><attribute name="message" layout="${message}" /><attribute name="trace_id" layout="${aspnet-TraceIdentifier:ignoreActivityId=true}" /><attribute name="user_id" layout="${aspnet-user-identity}" /><!--取得该条日志生产者名字--><attribute name="exception" layout="${exception:format=tostring}" /></target></targets><rules><logger name="*" minlevel="Info" writeTo="console"   ruleName="console" /><logger name="*" minlevel="Debug" writeTo="file" /></rules>
</nlog>

2.3 Program中修改

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using NLog.Web;
using System;namespace NlogDemo
{public static class Program{public static void Main(string[] args){var logger = NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();try{logger.Debug("init main");CreateHostBuilder(args).Build().Run();}catch (Exception ex){//NLog: catch setup errorslogger.Error(ex, "Stopped program because of exception");throw;}finally{NLog.LogManager.Shutdown();}}public static IHostBuilder CreateHostBuilder(string[] args) =>Host.CreateDefaultBuilder(args).ConfigureWebHostDefaults(webBuilder =>{webBuilder.UseStartup<Startup>();}).ConfigureLogging((_, loggerBuilder) =>{loggerBuilder.ClearProviders();loggerBuilder.SetMinimumLevel(LogLevel.Information);}).UseNLog();}
}

2.4 配置日志级别

{"Logging": {"LogLevel": {"Default": "Information","Microsoft": "Warning","Microsoft.Hosting.Lifetime": "Information"}}
}

2.5 控制器使用

        private readonly ILogger<HomeController> _logger;public HomeController(ILogger<HomeController> logger){_logger = logger;_logger.LogDebug(1, "NLog injected into HomeController");}[HttpGet]public string Get(){_logger.LogTrace("Trace");_logger.LogDebug("debug");_logger.LogInformation("info");_logger.LogWarning("warn");_logger.LogError("error");_logger.LogCritical("Critical");return default;}

查看输出的日志文件

3. 参考文档

https://github.com/NLog/NLog/wiki/Getting-started-with-ASP.NET-Core-5