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 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    }}

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: Index2020-12-29 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!

ITPub博客

NLog-ASP.NET Core 5入门