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nlog

            env.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 core

            loggerFactory.AddNLog();

            //add NLog.Web

            app.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();

        }