asp.net-core - appsettings.json 中的 NLog 配置而不是 .NET Core 中的 nlog.config

Question

NLog 文档解释了如何使用 nlog.config XML 文件为 .NET Core 应用程序配置 NLog。不过，我希望我的应用程序只有一个配置文件 - appsettings.json。对于 .NET Framework 应用，可以将 NLog 配置放入 app.config 或 web.config 中。是否可以以同样的方式将 NLog 配置放入 appsettings.json 中？

例如，我如何将这个配置示例放在 NLog documentation for ASP.NET Core 2 中进入appsettings.json？

<?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>

Answer 1

是的，这是可能的，但有最低版本要求。您必须使用 NLog.Extensions.Logging >= 1.5.0。请注意，对于 ASP.NET Core 应用程序，如果您安装 NLog.Web.AspNetCore >= 4.8.2，这将作为依赖项安装。

然后，您可以在 appsettings.json 中创建 NLog 部分，并使用以下代码加载它:

var config = new ConfigurationBuilder()
  .SetBasePath(System.IO.Directory.GetCurrentDirectory())
  .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true).Build();
NLog.Config.LoggingConfiguration nlogConfig = new NLogLoggingConfiguration(config.GetSection("NLog"));

例如，对于 ASP.NET Core 应用程序，Program.cs 中的 Main() 方法应如下所示:

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();
    }
}

可以通过 appsettings.json 中的以下设置来实现与问题中类似的配置:

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

编辑:感谢 Rolf Kristensen(他首先为 NLog 开发了此功能!)指出此 wiki 页面以及有关此功能的更多文档:https://github.com/NLog/NLog.Extensions.Logging/wiki/NLog-configuration-with-appsettings.json