log4net log file not being written when the app is deployed - wpf

Question

I have a WPF app that uses log4net. When I run it in Visual Studio, the log file is created in the Debug or Release folder as expected.
However, when I create an installer and run the installed app, the log file is not created. I added the following lines to the code...
string logFilePath = ((Hierarchy)LogManager.GetRepository())
.Root.Appenders.OfType<FileAppender>()
.FirstOrDefault()?.File;
using (StreamWriter sw = new StreamWriter(#"d:\log.log")) {
sw.WriteLine("Log file: " + logFilePath);
}
...to enable me to check that the log file was being written in the location I expected. It showed me that the log file was supposed to be written to C:\Program Files (x86)\Physio Diary\PhysioDiaryClient.log which is what I expected.
However, the file doesn't exist. Any idea why?
Here is the top of the App.config file...
<?xml version="1.0"
encoding="utf-8"?>
<configuration>
<configSections>
<section name="log4net"
type="log4net.Config.Log4NetConfigurationSectionHandler,Log4net" />
</configSections>
<log4net>
<appender name="RollingFileAppender"
type="log4net.Appender.RollingFileAppender">
<param name="File"
value="PhysioDiaryClient.log" />
<appendToFile value="true" />
<rollingStyle value="Size" />
<maxSizeRollBackups value="2" />
<maximumFileSize value="1MB" />
<staticLogFileName value="true" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %-7level %logger - %message%newline%exception" />
</layout>
</appender>
<root>
<level value="DEBUG" />
<appender-ref ref="RollingFileAppender" />
</root>
</log4net>
The bottom of the file looks like this...
<startup>
<supportedRuntime version="v4.0"
sku=".NETFramework,Version=v4.5.2" />
</startup>
</configuration>
The bits in between are all to do with the WCF services that the app uses.
Anyone any ideas?
Edit: As a test, I tried hard-coding the log file path in App.config to my D: drive (so it's hard-coded, and no question of a permissions issue), but the file still wasn't created.

Answer 1

Thanks to #dymanoid for pointing me in the right direction. The log4net docs are a bit weak in this area, but I found this answer that pointed out that you can use normal environment variables in the config file.
With the aid of this list of environment variables, I ended up with the following...
<param name="File"
value="${LOCALAPPDATA}\Physio Diary\PhysioDiaryClient.log" />
This correctly write the file to C:\Users\MyUsername\AppData\Local\Physio Diary\PhysioDiaryClient.log
Hope this helps someone.