在运行时更新NLog目标文件名

在我的应用程序中，我每天处理数千个文档.在某些情况下，我希望按文档记录一个日志.然后，我想为特定目标在运行时更改输出文件名(并且仅更改文件名).

In my application, I work on several thousand of document a day. I'd like, in some cases some logs, one log by document. Then I'd like for a specific target change the output filename (and only the filename) at runtime.

在网络上，我发现了如何通过编程来创建目标，我想通过编程来更新文件名.我尝试了下面的代码.我收到的错误是找不到LayoutRender'logDirectory'.

Around the web I found how to create a target by programming me I'd like just update a the filename by programming. I tried the code below. The error I receive is "LayoutRender cannot be found 'logDirectory'.

有什么主意吗?

谢谢

var target = (FileTarget)LogManager.Configuration.FindTargetByName("logfile");
target.FileName = "${logDirectory}/file2.txt";

LoggingConfiguration config = new LoggingConfiguration();
var asyncFileTarget = new AsyncTargetWrapper(target);
config.AddTarget("logfile", asyncFileTarget);

LogManager.Configuration = config;

配置文件为:

  <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <variable name="logDirectory" value="C:/MyLogs"/>
    <targets>
      <target name="logfile" xsi:type="File" layout="${date:format=dd/MM/yyyy HH\:mm\:ss.fff}|${level}|${stacktrace}|${message}" fileName="${logDirectory}/file.txt" />
    </targets>

    <rules>
      <logger name="*" minlevel="Info" writeTo="logfile" />
    </rules>    
  </nlog>