.NET Core 下使用 NLog 记录日志

NLog is a flexible and free logging platform for various .NET platforms, including .NET standard. NLog makes it easy to write to several targets. (database, file, console) and change the logging configuration on-the-fly.

• 官网：https://nlog-project.org
• 开源地址：https://github.com/NLog/NLog

最佳实践

控制台项目

在项目中添加组件包

Install-Package Microsoft.Extensions.Configuration.Json Install-Package NLog Install-Package NLog.Extensions.Logging 

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

<?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="internal-nlog.txt">    <!-- define various log targets -->   <targets>     <!-- write logs to file -->     <target xsi:type="File" name="allfile" fileName="nlog-all-${shortdate}.log"                  layout="${longdate}|${logger}|${uppercase:${level}}|${message} ${exception}" />       <target xsi:type="File" name="ownFile-web" fileName="nlog-own-${shortdate}.log"              layout="${longdate}|${logger}|${uppercase:${level}}|  ${message} ${exception}" />      <target xsi:type="Null" name="blackhole" />   </targets>    <rules>     <!--All logs, including from Microsoft-->     <logger name="*" minlevel="Trace" writeTo="allfile" />      <!--Skip Microsoft logs and so log only own logs-->     <logger name="Microsoft.*" minlevel="Trace" writeTo="blackhole" final="true" />     <logger name="*" minlevel="Trace" writeTo="ownFile-web" />   </rules> </nlog> 

添加一个类Runner.cs。

using Microsoft.Extensions.Logging;  namespace ConsoleDemo {     public class Runner     {         private readonly ILogger<Runner> _logger;          public Runner(ILogger<Runner> logger)         {             _logger = logger;         }          public void DoAction(string name)         {             _logger.LogDebug(20, "Doing hard work! {Action}", name);         }     } } 

通过注入的方式调用。

using Microsoft.Extensions.Configuration; using Microsoft.Extensions.DependencyInjection; using Microsoft.Extensions.Logging; using NLog; using NLog.Extensions.Logging; using System;  namespace ConsoleDemo {     class Program     {         static void Main(string[] args)         {             var logger = LogManager.GetCurrentClassLogger();              try             {                 var config = new ConfigurationBuilder().SetBasePath(System.IO.Directory.GetCurrentDirectory())                                                        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)                                                        .Build();                 var servicesProvider = BuildDi(config);                  using (servicesProvider as IDisposable)                 {                     var runner = servicesProvider.GetRequiredService<Runner>();                     runner.DoAction("Action1");                      Console.WriteLine("Press ANY key to exit");                     Console.ReadKey();                 }              }             catch (Exception ex)             {                 // NLog: catch any exception and log it.                 logger.Error(ex, "Stopped program because of exception");                 throw;             }             finally             {                 LogManager.Shutdown();             }         }          private static IServiceProvider BuildDi(IConfiguration config)         {             return new ServiceCollection()                .AddTransient<Runner>() // Runner is the custom class                .AddLogging(loggingBuilder =>                {                    // configure Logging with NLog                    loggingBuilder.ClearProviders();                    loggingBuilder.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);                    loggingBuilder.AddNLog(config);                })                .BuildServiceProvider();         }     } } 

运行项目，项目根目录下会多出两个日志文件。

AspNetCore项目

在项目中添加组件包

Install-Package NLog Install-Package NLog.Web.AspNetCore 

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

<?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="internal-nlog.txt">    <!-- define various log targets -->   <targets>     <!-- write logs to file -->     <target xsi:type="File" name="allfile" fileName="nlog-all-${shortdate}.log"                  layout="${longdate}|${logger}|${uppercase:${level}}|${message} ${exception}" />       <target xsi:type="File" name="ownFile-web" fileName="nlog-own-${shortdate}.log"              layout="${longdate}|${logger}|${uppercase:${level}}|  ${message} ${exception}" />      <target xsi:type="Null" name="blackhole" />   </targets>    <rules>     <!--All logs, including from Microsoft-->     <logger name="*" minlevel="Trace" writeTo="allfile" />      <!--Skip Microsoft logs and so log only own logs-->     <logger name="Microsoft.*" minlevel="Trace" writeTo="blackhole" final="true" />     <logger name="*" minlevel="Trace" writeTo="ownFile-web" />   </rules> </nlog> 

在Program.cs中使用NLog。

using Microsoft.AspNetCore.Hosting; using Microsoft.Extensions.Hosting; using Microsoft.Extensions.Logging; using NLog.Web; using System;  namespace WebDemo {     public class Program     {         public static void Main(string[] args)         {             var logger = NLog.Web.NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();              try             {                 logger.Debug("init main");                 CreateHostBuilder(args).Build().Run();             }             catch (Exception exception)             {                 //NLog: catch setup errors                 logger.Error(exception, "Stopped program because of exception");                 throw;             }             finally             {                 // Ensure to flush and stop internal timers/threads before application-exit (Avoid segmentation fault on Linux)                 NLog.LogManager.Shutdown();             }         }           public static IHostBuilder CreateHostBuilder(string[] args) =>             Host.CreateDefaultBuilder(args)                 .ConfigureWebHostDefaults(webBuilder =>                 {                     webBuilder.UseStartup<Startup>();                 })                 .ConfigureLogging(logging =>                 {                     logging.ClearProviders();                     logging.SetMinimumLevel(LogLevel.Trace);                 }).UseNLog();  // NLog: Setup NLog for Dependency injection     } } 

一切准备就绪，在任意地方写日志。

using Microsoft.AspNetCore.Mvc; using Microsoft.Extensions.Logging; using System; using System.Collections.Generic; using System.Linq;  namespace WebDemo.Controllers {     [ApiController]     [Route("[controller]")]     public class WeatherForecastController : ControllerBase     {         private static readonly string[] Summaries = new[]         {             "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"         };          private readonly ILogger<WeatherForecastController> _logger;          public WeatherForecastController(ILogger<WeatherForecastController> logger)         {             _logger = logger;         }           [HttpGet]         public IEnumerable<WeatherForecast> Get()         {             _logger.LogInformation("Hello, this is a Weather api!");              var rng = new Random();             return Enumerable.Range(1, 5).Select(index => new WeatherForecast             {                 Date = DateTime.Now.AddDays(index),                 TemperatureC = rng.Next(-20, 55),                 Summary = Summaries[rng.Next(Summaries.Length)]             }).ToArray();         }     } } 

调用上面api，查看日志文件。

更多用法，请查看官方wiki文档：https://github.com/NLog/NLog/wiki