1、安装引用NLog

使用NLog需要安装引用NLog.Extensions.Hosting，如配置文件使用类似 ${aspnet-request-url} 的配置，以aspnet-开头的则需要安装 NLog.Web.AspNetCore。

1）NLog.Extensions.Hosting

在Nuget管理程序中，搜索 "NLog.Extensions.Logging"，然后点击安装。

2）NLog.Web.AspNetCore

在Nuget管理程序中，搜索 "NLog.Web.AspNetCore"，然后点击安装。

相关文档：VS(Visual Studio)中Nuget的使用

2、NLog 配置文件

NLog 中配置文件可以使用XML和JSONSON格式的， 具体如下,

1）XML格式的配置

<?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="${currentdir}/Logs/error.txt" >

  <!-- enable asp.net core layout renderers -->
  <extensions>
    <add assembly="NLog.Web.AspNetCore"/>
  </extensions>
  <!-- the targets to write to -->
  <targets>
    <!-- File Target for all log messages with basic details -->
    <target xsi:type="File" name="allfile" fileName="${currentdir}/Logs/${shortdate}/${level}/${level}.txt" maxArchiveFiles="30"  enableArchiveFileCompression="true"
          concurrentWrites="true"
          keepFileOpen="true"
            layout="${longdate}|${event-properties:item=EventId:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}" />

    <!-- File Target for own log messages with extra web details using some ASP.NET core renderers -->
    <target xsi:type="File" name="ownFile-web" fileName="${currentdir}/Logs/${shortdate}/${level}/web.txt" maxArchiveFiles="30"
            layout="${longdate}|${event-properties:item=EventId:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}" />

    <!--Console Target for hosting lifetime messages to improve Docker / Visual Studio startup detection -->
    <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" />

  </targets>

  <!-- rules to map from logger name to target -->
  <rules>
    <!--All logs, including from Microsoft-->
    <logger name="*" minlevel="Error" writeTo="allfile" />

    <!--Output hosting lifetime messages to console target for faster startup detection -->
    <logger name="Microsoft.Hosting.Lifetime" minlevel="Info" writeTo="lifetimeConsole, ownFile-web" final="true" />

    <!--Skip non-critical Microsoft logs and so log only own logs (BlackHole) -->
    <logger name="Microsoft.*" maxlevel="Info" final="true" />
    <logger name="System.Net.Http.*" maxlevel="Info" final="true" />

    <logger name="*" minlevel="Trace" writeTo="ownFile-web" />
  </rules>
</nlog>

2）JSON配置文件

"NLog":{
    "internalLogLevel":"Info",
    "internalLogFile":"${currentdir}/Logs/error.log",
    "extensions": [
      { "assembly": "NLog.Extensions.Logging" },
      { "assembly": "NLog.Web.AspNetCore" }
    ],
    "targets":{
        "allfile":{
            "type":"File",
            "fileName":"${currentdir}/Logs/${shortdate}/${level}/${level}.log",
            "layout":"${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}"
        },
        "ownFile-web":{
            "type":"File",
            "fileName":"${currentdir}/Logs/${shortdate}/${level}/${level}.log",
            "layout":"${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}"
        }
    },
    "rules":[
        {
            "logger":"*",
            "minLevel":"Trace",
            "writeTo":"allfile"
        },
        {
            "logger":"Microsoft.*",
            "maxLevel":"Info",
            "final":"true"
        },
        {
            "logger":"*",
            "minLevel":"Trace",
            "writeTo":"ownFile-web"
        }
    ]
}

3、NLog配置及使用示例

下面是NLog的两种配置方式的使用，如下，

1）使用NLog.config配置使用

using Microsoft.OpenApi.Models;

using NLog.Web;

var builder = WebApplication.CreateBuilder(args);

// 配置NLog
builder.Logging.ClearProviders();
builder.Host.UseNLog();
builder.Services.AddControllers();


app.UseDefaultFiles();
app.UseStaticFiles();
app.MapControllers();

app.Run();

使用示例：

using Microsoft.AspNetCore.Mvc;
using UtilityWeb.API.Services;
using UtilityWeb.Core;

using UtilityWeb.Tools;

namespace UtilityWeb.API.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(Name = "GetWeatherForecast")]
        public IEnumerable<string> Get([FromServices] UtilityWebContext context,
            [FromServices] IUser userService,
            [FromServices] SwaggerService swaggerService)
        {
            _logger.LogError("error message");
            return new List<string>() { _logger.ToString() };
            
        }
    }
}

2）使用appsettings.json配置使用

public static void Main(string[] args)
{
    var config = new ConfigurationBuilder()
        .SetBasePath(System.IO.Directory.GetCurrentDirectory())
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true).Build();
    LogManager.Configuration = new NLogLoggingConfiguration(config.GetSection("NLog"));

    var logger = NLog.Web.NLogBuilder.ConfigureNLog(LogManager.Configuration).GetCurrentClassLogger();
    try
    {
        logger.Debug("Init main");
        CreateWebHostBuilder(args).Build().Run();
    }
    catch (Exception ex)
    {
        logger.Error(ex, "Stopped program because of exception");
    }
    finally {
        LogManager.Shutdown();
    }
}

4、NLog配置文件中布局渲染器(layout renderers)

布局渲染器（layout renderers）是一种机制，用于在日志消息中插入动态内容或格式化信息。它们允许您将变量、属性、日期时间信息等添加到日志消息中，以便更详细地记录和分析日志。布局渲染器是在${}中包含的占位符，会在运行时替换为实际值。

1）所有的布局参数

2）调用站点和堆栈跟踪

3）条件

4）上下文信息

5）计数器

6）日期和时间

7）编码和字符串转换

8）环境和配置文件

9）文件和目录

10）进程、线程和程序集

11）ASP.NET 和 ASP.NET Core