NLog appsetting default to relative path

Question

I want to use <appsetting> in NLog (the NLog.Extended NuGet package to be specific) to do something like this:

<variable name="logDir" value="${appsetting:name=RemoteLogDir:default=.\Log}" />

Where I set up RemoteLogDir when I publish my app, but fallback to a relative directory for local development. I've been able to get an absolute path to work, but that doesn't seem collaborator-friendly.

How can I get a relative path to work? Or do I need to submit a feature request?

Notes:

I'm using NLog 4.4.12 and NLog.Extended 4.0.0.1.
I'm using .NET 4.6.1 on Windows (10).
I've cross posted to the NLog repository.
The NLog.config is this:

<?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"
      xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd NLog.xsd"
      autoReload="true" throwExceptions="false">

  <variable xsi:type="NLogVariable" name="appLogName" value="MyApp"/>

  <variable xsi:type="NLogVariable" name="logDir" value="${appsetting:name=RemoteLogDir:default=\.\\Log}" />
  <variable xsi:type="NLogVariable" name="layout" value="${level:uppercase=true} | ${date:format=MM/dd/yyyy HH\:mm\:ss} | ${machinename} | ${windows-identity:domain=true} | ${callsite} ${newline}    ${message}${onexception:${newline}[EXCEPTION]${newline}${exception:format=tostring}}" />

  <variable xsi:type="NLogVariable" name="logFileName" value="${var:logDir}/${var:appLogName}_${date:format=yyyy-MM-dd}.txt" />
  <variable xsi:type="NLogVariable" name="archiveLogFileName" value="${var:logDir}/Archive/${var:appLogName}_Archived_{#}.txt" />

  <targets>
    <target name="singleFile" xsi:type="File"
              layout="${var:layout}"
              fileName="${var:logFileName}"
              concurrentWrites="true"
              keepFileOpen="true"
              archiveFileName="${var:archiveLogFileName}"
              archiveEvery="Day"
              archiveNumbering="Date"
              archiveDateFormat="yyyy-MM-dd_HH"
              maxArchiveFiles="30" />
  </targets>

  <rules>
    <logger name="*" minlevel="Trace" writeTo="singleFile" />
  </rules>
</nlog>

score 1 · Answer 1 · answered Oct 04 '17 at 21:59

TL;DR

<variable xsi:type="NLogVariable" name="logDir" value="${whenEmpty:whenEmpty=${basedir}/Log:inner=${appsetting:name=RemoteLogDir}}" />

Explanation

Indeed, the appsetting only accepts a string for the default value. However, you can emulate the desired functionality by supplying no default and using whenEmpty. When the app setting isn't set, the inner value will be counted as empty, so the whenEmpty value is rendered.

NLog appsetting default to relative path

1 Answers1