How to configure NLog for isolated plugin within host application

I'm working on a C# application, using the NLog library.

Log.Info() generates an output, which looks like the following:

2023-07-24 09:04:19.4423 | Info | Company.Customer.Manager.DoSomething | Some information

I would like to change that, and in the NLog.xml, I have found entries like:

<code>${longdate}|${level:uppercase=true}|${logger}|${message}</code>

... but there are some drawbacks:

1. I have found over 30 of those entries in NLog.xml, belonging to members with following names: M:NLog.Targets.TargetWithLayout.#ctor, P:NLog.Targets.TargetWithLayout.Layout, M:NLog.Targets.NetworkTarget.#ctor, and so on.
2. The entries have the following structure:

<member name="...">
    <summary>
        Some information
    </summary>
    <remarks>
        The default value of the layout is: 
        <code>${longdate}|${level:uppercase=true}|${logger}|${message}</code>
    </remarks>
</member>

=> basically it looks "just" like a remark.

So my questions are:

• Is it correct that the configuration of the NLog is somewhere in the remark of a member?
• If yes, how can I know which member?
• If no, where can I find that configuration?

Oh, before I forget: I don't have an NLog.config file.

Add a nlog.config -file to your project. Set the properties of the file to "Copy if Newer" to ensure it is copied to the output directory.

Then copy the some example configuration to your file. For example the one from the configuration file wiki

<?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 name="logfile" xsi:type="File" fileName="file.txt" />
        <target name="logconsole" xsi:type="Console" />
    </targets>

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

You can then start making changes, like changing the "layout" of the target:

<target 
  layout="${longdate}|${level:uppercase=true}|${logger}|${message}"
  name="logconsole" 
  xsi:type="Console" />

For a list of tags you can use in your layout, see layout renderers.

There are other ways to handle configuration, like putting the entire nlog-tag inside your app.config file. But the app.config can become kind of bloated, so I think it is better to use a separate file.

When creating a plugin that will live as guest in the house of the host-application, then it is not good style for the guest to replace the carpet in the living-room.

The plugin should not attempt to modify the NLog-configuration, as it can give unwanted side-effects for the host-application. When the plugin uses NLog.LogManager.GetCurrentClassLogger() then its output will depend on the NLog-configuration for the host-application.

If the plugin wants to have its own isolated NLog-configuration, then the plugin can initialize its own isolated NLog-LogFactory. Instead of using the NLog.LogManager. See also: https://github.com/NLog/NLog/wiki/Configure-component-logging#isolated-logfactory

The NLog.xml-file only contains XML-docs for Visual Studio Intellisense. NLog.dll doesn't use NLog.xml for anything.