Making NLog config file user define at run time

Question

I have a winForm app. I am using NLog for logging purpose. My config file is below. Can I make any paramter in this config file user define at run time. e.g for archiveAboveSize="4000" can I have a numericupdown in winform which can take input this value from user (so that 4000 can be 3000 or 5000) and then set this value in config file accordingly ?

<?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">

  <targets>
    <target xsi:type="File"
      name="file"
      layout="${longdate}|${level:uppercase=true}|${logger}|${message}"
      archiveAboveSize="4000"
      maxArchiveFiles="1"
      archiveFileName="${basedir}/log_archived.txt"
      fileName="log.txt" />
  </targets>

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

Answer 1

You can get target by name from NLog configuration and change settings at runtime:

var target = (FileTarget)LogManager.Configuration.FindTargetByName("file");
if (target != null)
    target.ArchiveAboveSize = 3000;

Unfortunately you can't update NLog configuration file this way - you should do that manually. You can use LINQ for that:

var nlogConfigFile = "NLog.config";
var xdoc = XDocument.Load(nlogConfigFile);
var ns = xdoc.Root.GetDefaultNamespace();
var fileTarget = xdoc.Descendants(ns + "target")
         .FirstOrDefault(t => (string)t.Attribute("name") == "file");
fileTarget.Attribute("archiveAboveSize").SetValue(3000);
xdoc.Save(nlogConfigFile);