1、创建一个新的ASP.NET Core项目

在Visual Studio 2019中。需要版本16.8+

2、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：

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

3、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="System.Net.Http.*" maxlevel="Info" final="true" /> <!-- BlackHole without writeTo --><logger name="*" minlevel="Trace" writeTo="ownFile-web" /></rules>
</nlog>

请注意，如果删除所有其他LoggingProviders（如控制台）并且仅使用NLog，则可能必须特别注意Hosting Lifetime Startup Messages。因为这可能导致托管环境（Visual Studio / Docker / Azure容器）看不到已启动的应用程序。

4、更新program.cs

更新program.cs

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using NLog.Web;namespace ASP.NET_Core_5_NLog_Example
{public 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 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(LogLevel.Trace);}).UseNLog();  // NLog: Setup NLog for Dependency injection}
}

5、配置appsettings.json / appsettings.Development.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": "*"
}

切记还要更新任何特定于环境的配置，以免引起任何意外。前任appsettings.Development.json

6、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();}

7、示例输出

启动ASP.NET Core网站时，我们得到两个文件：

2020-12-29 16:47:02.5291||DEBUG|ASP.NET_Core_5_NLog_Example.Program|init main |url: |action:
2020-12-29 16:47:03.5943|1|DEBUG|ASP.NET_Core_5_NLog_Example.Controllers.HomeController|NLog injected into HomeController |url: https://localhost/|action: Index
2020-12-29 16:47:03.5943||INFO|ASP.NET_Core_5_NLog_Example.Controllers.HomeController|Hello, this is the index! |url: https://localhost/|action: Index

2020-12-29 16:47:02.5291||DEBUG|ASP.NET_Core_5_NLog_Example.Program|init main
2020-12-29 16:47:03.5260||INFO|Microsoft.Hosting.Lifetime|Application started. Press Ctrl+C to shut down.
2020-12-29 16:47:03.5260||INFO|Microsoft.Hosting.Lifetime|Hosting environment: Development
2020-12-29 16:47:03.5260||INFO|Microsoft.Hosting.Lifetime|Content root path: D:\nlog\NLog.Web\examples\ASP.NET Core 5\ASP.NET Core 5 NLog Example
2020-12-29 16:47:03.5943|1|DEBUG|ASP.NET_Core_5_NLog_Example.Controllers.HomeController|NLog injected into HomeController
2020-12-29 16:47:03.5943||INFO|ASP.NET_Core_5_NLog_Example.Controllers.HomeController|Hello, this is the index!