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。NLog使写入多个目标变得容易。（数据库，文件，控制台）并即时更改日志记录配置。

NLog支持结构化和传统日志记录。

NLog的重点是：高性能，易于使用，易于扩展和灵活配置。

特征

易于配置

通过配置文件和以编程方式，NLog都非常易于配置。即使不重新启动应用程序，也可以更改配置。

可模板化

每个日志消息都可以使用各种布局渲染进行模板化

可扩展的

即使NLog具有目标和预定义的布局，您也可以编写自定义目标或传递自定义值

结构化日志

全面支持结构化日志记录

目标

目标用于显示，存储日志消息或将日志消息传递到另一个目标。NLog可以为每个日志消息动态写入多个目标之一。

现成提供了30多个目标，其中包括：

文档

使用自动文件命名和归档功能，将日志写入任意数量的文件。默认情况下，NLog不会锁定您的文件。

事件记录日志

写入事件日志本地或远程

数据库

将日志存储在.NET支持的数据库中

控制台

实时写入命令行控制台，包括消息的颜色编码

电子邮件

每当出现应用程序错误时，您都可以发送电子邮件

ASP.NET核心记录

将日志消息写入ASP.NET Core日志记录

还有一些包装器目标，它们提供缓冲，负载平衡，故障转移情况，异步写入和更多方案。目标的完整列表在配置选项页面上。如果找不到适合您需求的目标，则可以轻松编写自定义目标。

支持

NLog支持以下平台：

.NET Framework 3.5、4、4.5-4.8
.NET Framework 4客户端配置文件
Xamarin Android
Xamarin iOs
Windows Phone 8
Silverlight 4和5
单声道4
ASP.NET 4（NLog.Web程序包）
ASP.NET Core（NLog.Web.AspNetCore程序包）
.NET Core（NLog.Extensions.Logging程序包）
.NET Standard 1.x-NLog 4.5
.NET Standard 2.x-NLog 4.5
UWP-NLog 4.5
入门

创建一个新的ASP.NET Core项目

在Visual Studio 2019中。

手动或使用NuGet在csproj中添加依赖项

安装最新版本：

NLog.Web.AspNetCore 4.9+
如有可能，更新NLog软件包

在csproj中：

<PackageReference Include="NLog.Web.AspNetCore" Version="4.9.0" />
<PackageReference Include="NLog" Version="4.6.7" />

创建一个nlog.config文件。

在项目的根目录中创建nlog.config（全部小写）文件。

我们使用以下示例：

<?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="Info"internalLogFile="c:\temp\internal-nlog.txt"><!-- enable asp.net core layout renderers --><extensions><add assembly="NLog.Web.AspNetCore"/></extensions><!-- the targets to write to --><targets><!-- write logs to file  --><target xsi:type="File" name="allfile" fileName="c:\temp\nlog-all-${shortdate}.log"layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}" /><!-- another file log, only own logs. Uses some ASP.NET core renderers --><target xsi:type="File" name="ownFile-web" fileName="c:\temp\nlog-own-${shortdate}.log"layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}" /></targets><!-- rules to map from logger name to target --><rules><!--All logs, including from Microsoft--><logger name="*" minlevel="Trace" writeTo="allfile" /><!--Skip non-critical Microsoft logs and so log only own logs--><logger name="Microsoft.*" maxlevel="Info" final="true" /> <!-- BlackHole without writeTo --><logger name="*" minlevel="Trace" writeTo="ownFile-web" /></rules>
</nlog>

启用复制到bin文件夹

为nlog.config启用复制到bin文件夹

或.csproj手动编辑文件并添加：

<ItemGroup><Content Update="nlog.config" CopyToOutputDirectory="PreserveNewest" /></ItemGroup>

更新program.cs

using System;
using NLog.Web;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Hosting;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 errorslogger.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(Microsoft.Extensions.Logging.LogLevel.Trace);}).UseNLog();  // NLog: Setup NLog for Dependency injection

配置appsettings.json

中指定的日志记录配置appsettings.json会覆盖对的任何调用SetMinimumLevel。因此"Default":，请根据您的需要删除或正确调整它。

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

写日志

将ILogger注入您的控制器中：

using Microsoft.Extensions.Logging;public class HomeController : Controller
{private readonly ILogger<HomeController> _logger;public HomeController(ILogger<HomeController> logger){_logger = logger;_logger.LogDebug(1, "NLog injected into HomeController");}public IActionResult Index(){_logger.LogInformation("Hello, this is the index!");return View();}

输出示例

启动ASP.NET Core网站时，我们得到两个文件：

nlog-own-2019-10-14.log
2019-10-14 23:15:09.3898|0|DEBUG|ASP.NET_Core_3___VS2019.Program|init main |url: |action: |ASP.NET_Core_3___VS2019.Program.Main
2019-10-14 23:15:11.3867|1|DEBUG|ASP.NET_Core_3___VS2019.Controllers.HomeController|NLog injected into HomeController |url: https://localhost/|action: Index|ASP.NET_Core_3___VS2019.Controllers.HomeController..ctor
2019-10-14 23:15:11.3867|0|INFO|ASP.NET_Core_3___VS2019.Controllers.HomeController|Hello, this is the index! |url: htt

nlog-all-2019-10-14.log
2019-10-14 23:15:09.3898|0|DEBUG|ASP.NET_Core_3___VS2019.Program|init main 
2019-10-14 23:15:10.9142|0|INFO|Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager|User profile is available. Using 'C:\Users\Julian\AppData\Local\ASP.NET\DataProtection-Keys' as key repository and Windows DPAPI to encrypt keys at rest. 
2019-10-14 23:15:11.2680|0|INFO|Microsoft.Hosting.Lifetime|Application started. Press Ctrl+C to shut down. 
2019-10-14 23:15:11.2680|0|INFO|Microsoft.Hosting.Lifetime|Hosting environment: Development 
2019-10-14 23:15:11.2680|0|INFO|Microsoft.Hosting.Lifetime|Content root path: D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019 
2019-10-14 23:15:11.3238|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/   
2019-10-14 23:15:11.3434|0|INFO|Microsoft.AspNetCore.Routing.EndpointMiddleware|Executing endpoint 'ASP.NET_Core_3___VS2019.Controllers.HomeController.Index (ASP.NET Core 3 - VS2019)' 
2019-10-14 23:15:11.3867|3|INFO|Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker|Route matched with {action = "Index", controller = "Home"}. Executing controller action with signature Microsoft.AspNetCore.Mvc.IActionResult Index() on controller ASP.NET_Core_3___VS2019.Controllers.HomeController (ASP.NET Core 3 - VS2019). 
2019-10-14 23:15:11.3867|1|DEBUG|ASP.NET_Core_3___VS2019.Controllers.HomeController|NLog injected into HomeController 
2019-10-14 23:15:11.3867|0|INFO|ASP.NET_Core_3___VS2019.Controllers.HomeController|Hello, this is the index! 
2019-10-14 23:15:11.4161|1|INFO|Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor|Executing ViewResult, running view Index. 
2019-10-14 23:15:11.5831|4|INFO|Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor|Executed ViewResult - view Index executed in 167.626ms. 
2019-10-14 23:15:11.5831|2|INFO|Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker|Executed action ASP.NET_Core_3___VS2019.Controllers.HomeController.Index (ASP.NET Core 3 - VS2019) in 196.6052ms 
2019-10-14 23:15:11.5831|1|INFO|Microsoft.AspNetCore.Routing.EndpointMiddleware|Executed endpoint 'ASP.NET_Core_3___VS2019.Controllers.HomeController.Index (ASP.NET Core 3 - VS2019)' 
2019-10-14 23:15:11.5910|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 267.9366ms 200 text/html; charset=utf-8 
2019-10-14 23:15:11.6171|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/lib/jquery/dist/jquery.min.js   
2019-10-14 23:15:11.6171|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/css/site.css   
2019-10-14 23:15:11.6171|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/lib/bootstrap/dist/css/bootstrap.min.css   
2019-10-14 23:15:11.6365|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/lib/bootstrap/dist/js/bootstrap.bundle.min.js   
2019-10-14 23:15:11.6365|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/js/site.js?v=4q1jwFhaPaZgr8WAUSrux6hAuh0XDg9kPS3xIVq36I0   
2019-10-14 23:15:11.6627|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/js/site.js'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\js\site.js' 
2019-10-14 23:15:11.6627|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/css/site.css'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\css\site.css' 
2019-10-14 23:15:11.6627|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 28.7787ms 200 application/javascript 
2019-10-14 23:15:11.6696|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 52.4825ms 200 text/css 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/lib/bootstrap/dist/js/bootstrap.bundle.min.js'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\lib\bootstrap\dist\js\bootstrap.bundle.min.js' 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/lib/bootstrap/dist/css/bootstrap.min.css'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\lib\bootstrap\dist\css\bootstrap.min.css' 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/lib/jquery/dist/jquery.min.js'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\lib\jquery\dist\jquery.min.js' 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 50.937400000000004ms 200 application/javascript 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 70.65100000000001ms 200 text/css 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 71.51610000000001ms 200 application/javascript