.NET Core 7中如何在运行时通过NLog获取目标文件完整路径？

我有一个在.NET Core 6中运行正常的控制台应用，当前正在将其迁移至刚发布的.NET Core 7，其他功能均正常，但动态获取NLog目标文件路径的部分出现问题。

NLog.config配置内容 #

<?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="Warn"
  internalLogFile="internal-CimplDataLoader.log">
  
<extensions>
    <add assembly="NLog.Extensions.Logging" />
</extensions>

<targets>
  <target xsi:type="File" name="allfile" fileName="${shortdate}.log"
              layout="${longdate}|${event-properties:item=EventId.Id}|${logger}|${uppercase:${level}}|${message} ${exception}"
              keepFileOpen="false"/>
</targets>

<rules>
  <!--All logs, including from Microsoft-->
  <logger name="*" minlevel="Trace" writeTo="allfile" />
</rules>
</nlog>

.NET Core 6中可用的代码 #

if (LogManager.Configuration != null)
{
    Target target = LogManager.Configuration.FindTargetByName("allfile");
    var logEventInfo = new LogEventInfo { TimeStamp = DateTime.Now };
    FileTarget? fileTarget;

    // Unwrap the target if necessary.
    if (target is not WrapperTargetBase wrapperTarget)
        fileTarget = target as FileTarget;
    else
        fileTarget = wrapperTarget.WrappedTarget as FileTarget;

    if (fileTarget != null)
    {
        string fileName = fileTarget.FileName.Render(logEventInfo);
        string LogPath = Path.GetDirectoryName(fileName)!;

        /* Work with LogPath */
    }
    else
    {
        _logger.LogError("Unable to get NLog \"allfile\" base directory.");
    }
}
else
{
    _logger.LogError("Unable to read NLog configuration.");
}

这段代码在.NET Core 7中失效，因为LogManager.Configuration始终为null。请问是否有办法在.NET Core 7中仍能动态获取该路径？

解决方案 #

1. 通过依赖注入容器获取NLog配置

在.NET 7中，若使用依赖注入方式配置NLog，LogManager.Configuration不会自动初始化，需从DI容器中提取配置：

using NLog;
using NLog.Extensions.Logging;
using Microsoft.Extensions.Logging;
using System.IO;

// 从已构建的ServiceProvider中获取ILoggerFactory
var loggerFactory = serviceProvider.GetRequiredService<ILoggerFactory>();
var nLogFactory = loggerFactory as NLogLoggerFactory;

if (nLogFactory != null)
{
    var config = nLogFactory.Configuration;
    Target target = config.FindTargetByName("allfile");
    var logEventInfo = new LogEventInfo { TimeStamp = DateTime.Now };
    FileTarget? fileTarget;

    if (target is not WrapperTargetBase wrapperTarget)
        fileTarget = target as FileTarget;
    else
        fileTarget = wrapperTarget.WrappedTarget as FileTarget;

    if (fileTarget != null)
    {
        string fileName = fileTarget.FileName.Render(logEventInfo);
        string logPath = Path.GetDirectoryName(fileName)!;

        // 处理日志路径逻辑
    }
    else
    {
        _logger.LogError("无法获取NLog \"allfile\"目标的基础目录。");
    }
}

2. 手动加载NLog配置文件

若未使用依赖注入，可手动加载配置文件初始化LogManager.Configuration：

using NLog;
using NLog.Config;
using System.IO;

var config = new XmlLoggingConfiguration("NLog.config");
LogManager.Configuration = config;

// 后续可复用原.NET 6中的代码逻辑
if (LogManager.Configuration != null)
{
    // ... 原代码逻辑
}

3. 确认NLog在.NET 7中的初始化配置

检查Program.cs中的NLog初始化代码，确保配置正确：

var builder = WebApplication.CreateBuilder(args);

// 清除默认日志提供器，添加NLog
builder.Logging.ClearProviders();
builder.Logging.SetMinimumLevel(LogLevel.Trace);
builder.Services.AddNLog();

var app = builder.Build();

// ... 应用其他逻辑

内容的提问来源于stack exchange，提问作者pdube