NLog是一个基于.NET平台编写的类库，我们可以使用NLog在应用程序中添加极为完善的跟踪调试代码。

NLog是一个简单灵活的.NET日志记录类库。通过使用NLog，我们可以在任何一种.NET语言中输出带有上下文的（contextual information）调试诊断信息，根据喜好配置其表现样式之后发送到一个或多个输出目标（target）中。

NLog的API非常类似于log4net，且配置方式非常简单。NLog使用路由表（routing table）进行配置，但log4net却使用层次性的appender配置，这样就让NLog的配置文件非常容易阅读，并便于今后维护。

<?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"autoReload="true"internalLogLevel="Warn"internalLogFile="c:\temp\internal-nlog.txt"><!-- 加载ASP.NET Core插件 --><extensions><add assembly="NLog.Web.AspNetCore"/></extensions><!-- 输出目的地 --><targets><!-- 输出到文件,这个文件记录所有日志 --><target xsi:type="File" name="allfile" fileName="c:\temp\nlog-all-${shortdate}.log"layout="${longdate}|${event-properties:item=EventId.Id}|${logger}|${uppercase:${level}}|${message} ${exception}" /><!-- 另外一个日志记录文件,户口也跳过Microsoft开头相关日志信息 --><target xsi:type="File" name="ownFile-web" fileName="c:\temp\nlog-own-${shortdate}.log"layout="${longdate}|${event-properties:item=EventId.Id}|${logger}|${uppercase:${level}}|  ${message} ${exception}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}" /><!-- write to the void aka just remove --><target xsi:type="Null" name="blackhole" /></targets><!-- 写入目的地的规则 --><rules><!--全部记录,包括Microsoft开头的相关日志信息--><logger name="*" minlevel="Trace" writeTo="allfile" /><!--跳过Microsoft开头的相关日志信息--><logger name="Microsoft.*" minlevel="Trace" writeTo="blackhole" final="true" /><logger name="*" minlevel="Trace" writeTo="ownFile-web" /></rules>
</nlog>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using NLog.Extensions.Logging;
using NLog.Web;namespace NlogDemo
{public class Startup{public Startup(IConfiguration configuration,IHostingEnvironment env){Configuration = configuration;//配置nlogenv.ConfigureNLog("nlog.config");}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddMvc();}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory){//把nlog添加到.net coreloggerFactory.AddNLog();//add NLog.Webapp.AddNLogWeb();if (env.IsDevelopment()){app.UseBrowserLink();app.UseDeveloperExceptionPage();}else{app.UseExceptionHandler("/Home/Error");}app.UseStaticFiles();app.UseMvc(routes =>{routes.MapRoute(name: "default",template: "{controller=Home}/{action=Index}/{id?}");});}}
}

public class HomeController : Controller{private readonly ILogger<HomeController> _logger;public HomeController(ILogger<HomeController> logger){_logger = logger;}public IActionResult Index(){_logger.LogInformation("Index page says hello");return View();}