log4net logs PlatformNotSupportedException on Android

[arunjose696]

I'm experiencing the same problem described in issue #153 . I've put together a minimal example using a basic .NET MAUI app to reproduce it.

In this simple MAUI app, log4net doesn't seem to work. All I did was create a new .NET MAUI project in Visual Studio and install log4net via the NuGet package manager. Then, inside MauiProgram.CreateMauiApp(), I attempted to use log4net for logging. Even when I use BasicConfigurator—which, according to https://logging.apache.org/log4net/release/manual/configuration.html shouldn't require any XML configuration, it still fails.

Find below my code and exception

using Microsoft.Extensions.Logging;
using log4net;
using log4net.Config;
namespace MauiApp3
{
    public static class MauiProgram
    {
        private static readonly ILog log = LogManager.GetLogger(typeof(MauiProgram));
        public static MauiApp CreateMauiApp()
        {

            BasicConfigurator.Configure();
            log.Info("Entering application.");
            var builder = MauiApp.CreateBuilder();
            builder
                .UseMauiApp<App>()
                .ConfigureFonts(fonts =>
                {
                    fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                    fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
                });

#if DEBUG
    		builder.Logging.AddDebug();
#endif

            return builder.Build();
        }
    }
}

In the debug logs I see this exception .

[DOTNET] log4net:ERROR Exception while reading ConfigurationSettings. Check your .config file is well formed XML.
[0:] log4net:ERROR Exception while reading ConfigurationSettings. Check your .config file is well formed XML.
[DOTNET] System.Configuration.ConfigurationErrorsException: Configuration system failed to initialize
[DOTNET]  ---> System.PlatformNotSupportedException: Operation is not supported on this platform.
[DOTNET]    at System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig)
[DOTNET]    at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig)
[DOTNET]    at System.Configuration.ClientConfigurationHost.get_ConfigPaths()
[DOTNET]    at System.Configuration.ClientConfigurationHost.GetStreamName(String configPath)
[DOTNET]    at System.Configuration.ClientConfigurationHost.get_IsAppConfigHttp()
[DOTNET]    at System.Configuration.Internal.DelegatingConfigHost.get_IsAppConfigHttp()
[DOTNET]    at System.Configuration.ClientConfigurationSystem..ctor()
[DOTNET]    at System.Configuration.ConfigurationManager.EnsureConfigurationSystem()
[DOTNET]    --- End of inner exception stack trace ---
[DOTNET]    at System.Configuration.ConfigurationManager.PrepareConfigSystem()
[DOTNET]    at System.Configuration.ConfigurationManager.GetSection(String sectionName)
[DOTNET]    at System.Configuration.ConfigurationManager.get_AppSettings()
[DOTNET]    at log4net.Util.SystemInfo.GetAppSetting(String key) in D:\Git\apache\logging-log4net\src\log4net\Util\SystemInfo.cs:line 651
[0:] System.Configuration.ConfigurationErrorsException: Configuration system failed to initialize
 ---> System.PlatformNotSupportedException: Operation is not supported on this platform.
   at System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig)
   at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig)
   at System.Configuration.ClientConfigurationHost.get_ConfigPaths()
   at System.Configuration.ClientConfigurationHost.GetStreamName(String configPath)
   at System.Configuration.ClientConfigurationHost.get_IsAppConfigHttp()
   at System.Configuration.Internal.DelegatingConfigHost.get_IsAppConfigHttp()
   at System.Configuration.ClientConfigurationSystem..ctor()
   at System.Configuration.ConfigurationManager.EnsureConfigurationSystem()
   --- End of inner exception stack trace ---
   at System.Configuration.ConfigurationManager.PrepareConfigSystem()
   at System.Configuration.ConfigurationManager.GetSection(String sectionName)
   at System.Configuration.ConfigurationManager.get_AppSettings()
   at log4net.Util.SystemInfo.GetAppSetting(String key) in D:\Git\apache\logging-log4net\src\log4net\Util\SystemInfo.cs:line 651
[DOTNET] log4net:ERROR Exception while reading ConfigurationSettings. Check your .config file is well formed XML.
[0:] log4net:ERROR Exception while reading ConfigurationSettings. Check your .config file is well formed XML.
[DOTNET] System.Configuration.ConfigurationErrorsException: Configuration system failed to initialize
[DOTNET]  ---> System.PlatformNotSupportedException: Operation is not supported on this platform.
   --- End of inner exception stack trace ---
   at System.Configuration.ConfigurationManager.PrepareConfigSystem()
   at System.Configuration.ConfigurationManager.GetSection(String sectionName)
   at System.Configuration.ConfigurationManager.get_AppSettings()
   at log4net.Util.SystemInfo.GetAppSetting(String key) in D:\Git\apache\logging-log4net\src\log4net\Util\SystemInfo.cs:line 651
[DOTNET]    at System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig)
[DOTNET]    at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig)
[DOTNET]    at System.Configuration.ClientConfigurationHost.get_ConfigPaths()
[DOTNET]    at System.Configuration.ClientConfigurationHost.GetStreamName(String configPath)
[DOTNET]    at System.Configuration.ClientConfigurationHost.get_IsAppConfigHttp()
[DOTNET]    at System.Configuration.Internal.DelegatingConfigHost.get_IsAppConfigHttp()
[DOTNET]    at System.Configuration.ClientConfigurationSystem..ctor()
[DOTNET]    at System.Configuration.ConfigurationManager.EnsureConfigurationSystem()
[DOTNET]    --- End of inner exception stack trace ---
[DOTNET]    at System.Configuration.ConfigurationManager.PrepareConfigSystem()
[DOTNET]    at System.Configuration.ConfigurationManager.GetSection(String sectionName)
[DOTNET]    at System.Configuration.ConfigurationManager.get_AppSettings()
[DOTNET]    at log4net.Util.SystemInfo.GetAppSetting(String key) in D:\Git\apache\logging-log4net\src\log4net\Util\SystemInfo.cs:line 651

It also fails when I use XmlConfigurator.Configure() and provide that the config file must be copied as is to the target directory (and using the default build action for config files) as mentioned in #153 (comment)

I use maui -> 9.0.4
log4net-> 3.0.4
.net -> 9

[arunjose696]

@FreeAndNil any suggestions?

[FreeAndNil]

@arunjose696 can you post your config file?
Sometimes Check your .config file is well formed XML. means your config file is not well formed ;-)

[arunjose696]

Do I even need a config file in BasicConfigurator.Configure()?;, I was using BasicConfigurator.Configure() to make the reproducer minimal so for this case I did not use a config file.

I also tried using the below example with XmlConfigurator.Configure

<log4net>
    <appender name="Console" type="log4net.Appender.ConsoleAppender">
        <layout type="log4net.Layout.PatternLayout">
            <!-- Pattern to output the caller's file name and line number -->
            <conversionPattern value="%5level [%thread] (%file:%line) - %message%newline" />
        </layout>
    </appender>
    
    <appender name="RollingFile" type="log4net.Appender.RollingFileAppender">
        <file value="example.log" />
        <appendToFile value="true" />
        <maximumFileSize value="100KB" />
        <maxSizeRollBackups value="2" />
 
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%level %thread %logger - %message%newline" />
        </layout>
    </appender>
    
    <root>
        <level value="DEBUG" />
        <appender-ref ref="Console" />
        <appender-ref ref="RollingFile" />
    </root>
</log4net>

[FreeAndNil]

This is a valid log4net configuration, but not a valid app.config.
Can you add a configuration element and a config section element?

[arunjose696]

I am using MAUI with dotnet 9, there is no app.config file,

From what I understand from here app.config is a older style https://learn.microsoft.com/en-us/answers/questions/1510926/why-do-some-c-applications-have-an-app-config-file

Do you have any documentation on how to do the cofiguration for MAUI apps?

[FreeAndNil]

You just add a config file via "Add ..." and paste the content from #153 (comment)

[arunjose696]

I tried adding the app.config file still I see the Exception

[FreeAndNil]

Can you zip your test project and post it here?

[arunjose696]

Here is the zip file, There are just very minor changes from the basic MAUI app created in visual studio.

MauiAppLog4net.zip

[FreeAndNil]

Your app runs fine on my PC (Win11 24H2 / VS 17.13.6).
For another test I have added a file appender and moved from BasicConfigurator to XmlConfigurator.

2025-04-26 21:11:18,276| INFO | Entering application.

Please take a look at the adjusted sample:

MauiApp3.zip

[arunjose696]

Thank you for the response. I also tried using this zip file.

The code runs perfectly fine when executed on the Windows machine in Visual Studio, but the exception only occurs when I try running it on an Android device or emulator. I change the run configuration in Visual Studio from the Windows machine to the Android emulator. Could you please try running it on an Android emulator in Visual Studio?

Apologies for not mentioning earlier that I am running on Android.

[FreeAndNil]

You need to use xml (config) files for android.
log4net supports xml files on all plattforms.

See the attached example.

MauiApp4.zip

More details for log4net config files can be found here