Develop Reference

Log4net error - patternstring not working

I am creating a logging component using log4net in my project. I've created an xml file to configure the log4net settings including an append-er and logger definition. I'm using PatternString to pick up properties' value from the appsetting.config file. However when I build and run the project, it throws the following error:
log4net:ERROR Undefined level [%property{Level}] on Logger [Test].
Does anyone know what might be causing it?
XML:
<?xml version="1.0" encoding="UTF-8" ?>
<log4net>
<logger name="Test">
<level type="log4net.Util.PatternString" value="%property{Level}" />
<appender-ref ref="JsonFileAppender" />
</logger>
</log4net>
appsetting.config:
<appSettings>
<add key="Level" value="ALL"/>
</appSettings>
In case it's useful the log4net version is: version:2.0.8

Good question!
I learnt from this, a lot.
Please don't forget to call this method before start logging.
log4net.Config.XmlConfigurator.Configure();
app.config is.
if you need apply pattern, use <layout> element.
and if you want to use some value from "appSettings",
use like this, %appSetting{Environment}
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>
<log4net>
<appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender" >
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %-5level %logger [%ndc] - %message%newline" />
</layout>
</appender>
<root>
<level value="%appSetting{Environment}" />
<appender-ref ref="ConsoleAppender" />
</root>
</log4net>
<appSettings>
<add key="Environment" value="INFO" />
<!-- this is optional flag.-->
<add key="log4net.Internal.Debug" value="True" />
</appSettings>
</configuration>
Here is where I learned
Accessing appSettings config values from log4net config section
https://logging.apache.org/log4net/release/manual/configuration.html
https://www.paraesthesia.com/archive/2010/11/12/log4net-appsettings-keys.aspx/

The reason for this error is because the level of a logger can't be configured via a PatternString.
The <level> elements expects a wellknown value, like eg. ALL, DEBUG, INFO, WARN, ERROR,
eg.:
<logger name="Test">
<level value="All" />
</logger>
From your setup I read that you are trying to apply a setting from AppSettings.config upon the log level of a logger in your Log4net configuration.
As explained above, this can't be done.
Either keep all Log4net related settings within its own xml - in the end it is also configuration.
Or set the level programmatically;
you will have to translate the string value in appsettings.config to a Level yourself.
logger = LogManager.GetLogger("Test");
Level level = // Parse from ConfigurationManager.AppSettings["Level"]
((Logger)logger.Logger).Level = level;

How to get Log4Net to use app.config

The Story: I have a WinForms application with multiple assemblies - MainApp and Utilities. I use Utilities for my logging via log4net. All is fine with the world if I use a separate config file for log4net (aka log4net.config) - no issues.
However, IT staff finds it challenging to tweak two .config files (MainApp.exe.config and log4net.config). So, I'm trying to add my log4net config settings into my app.config file. Not having any luck.
I've tried several solutions posted in this forum. This one seemed to experience the same error I get:
log4net configuration - failed to find section
I've tried putting this line in my Utilities:AssemblyInfo.cs
[assembly: log4net.Config.XmlConfigurator(ConfigFile = "MainApp.exe.config", Watch = false)]
In my Utilities module where log4net is referenced, I have this:
const string TEMP_VARIABLE = "TEMP";
string tempDir = Environment.GetEnvironmentVariable( TEMP_VARIABLE );
StringBuilder userTempDirLogFile = new StringBuilder( tempDir );
userTempDirLogFile.Append( #"\" );
userTempDirLogFile.Append( Environment.MachineName );
userTempDirLogFile.Append( "_MAIN_" );
userTempDirLogFile.Append( DateTime.Now.DayOfWeek );
userTempDirLogFile.Append( ".log" );
log4net.GlobalContext.Properties["MainLogFileName"] = userTempDirLogFile.ToString();
StringBuilder utilityLogFile = ( userTempDirLogFile.Replace( "_MAIN_", "_UTILITIES_" ) );
log4net.GlobalContext.Properties["UtilityLogFileName"] = utilityLogFile.ToString();
log4net.Config.XmlConfigurator.Configure();
_mainLogger = LogManager.GetLogger( "MAIN" );
_mainLogger gets this error message:
log4net:ERROR XmlConfigurator: Failed to find configuration section 'log4net' in the application's .config file. Check your .config file for the <log4net> and <configSections> elements. The configuration section should look like: <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
I noticed in log4net source code that log4net.Config.XmlConfigurator.Configure() calls Assembly.GetCallingAssembly(). I've verified that GetCallingAssembly() is indeed MainApp. My program directory contains all necessary files.
This is my app.config
<?xml version="1.0"?>
<configuration>
<!-- configSections MUST be first! -->
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
</configSections>
<log4net>
<appender name="MainLogFile" type="log4net.Appender.RollingFileAppender">
<file type="log4net.Util.PatternString" value="%property{MainLogFileName}"/>
<appendToFile value="false" />
<maximumFileSize value="20MB" />
<maxSizeRollBackups value="3" />
<param name="Encoding" value="unicodeFFFE" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date{ISO8601} %property{messageId} %-5level %message%newline" />
</layout>
<filter type="log4net.Filter.LevelRangeFilter">
<param name="LevelMin" value="ALL" />
<param name="LevelMax" value="OFF" />
</filter>
</appender>
<appender name="UtilityLogFile" type="log4net.Appender.RollingFileAppender">
<file type="log4net.Util.PatternString" value="%property{UtilityLogFileName}"/>
<appendToFile value="false" />
<maximumFileSize value="20MB" />
<maxSizeRollBackups value="3" />
<param name="Encoding" value="unicodeFFFE" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date{ISO8601} %property{messageId} %-5level %message%newline" />
</layout>
<filter type="log4net.Filter.LevelRangeFilter">
<param name="LevelMin" value="ALL" />
<param name="LevelMax" value="OFF" />
</filter>
</appender>
<logger name="MAIN">
<level value="DEBUG" />
<appender-ref ref="MainLogFile" />
</logger>
<logger name="UTILITY">
<level value="DEBUG" />
<appender-ref ref="UtilityLogFile" />
</logger>
</log4net>
<startup>
<!-- Leave sku out so that both 4.0 and 4.5 are supported -->
<supportedRuntime version="v4.0" />
</startup>
<system.windows.forms jitDebugging="true" />
<system.diagnostics>
<trace useGlobalLock="false" />
</system.diagnostics>
<appSettings>
<add key="PRINT_CALL_STACK" value="false"/>
<add key="TRACK_PERFORMANCE" value="false"/>
<add key="USING_TEST_MODE" value="false"/>
<add key="WAIT_FOR_LOGON" value="0"/>
</appSettings>
</configuration>
I figure I'm missing something, but no clue as to what. Thanks for your time.
Note: using VS2013 and log4net 1.2.13.0. Solution targets .NET 4.0 full and x86.

If you want to put everything in your app.config, make sure you have this in the AssemblyInfo.cs:
[assembly: log4net.Config.XmlConfigurator(ConfigFileExtension = "config", Watch = true)]
true or false can be changed if you want to monitor dynamically or not the config file for changes.
and in your config file, make sure you have the appropriate sections. For example in mine I have:
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>
<log4net>
<appender name="FileAppender" type="log4net.Appender.FileAppender">
<param name="file" value="logs/App.log"/>
<param name="appendToFile" value="True"/>
<param name="encoding" value="utf-8"/>
<param name="staticLogFileName" value="False"/>
<param name="RollingStyle" value="Size"/>
<param name="MaxSizeRollBackups" value="1"/>
<param name="MaxFileSize" value="10485760"/>
<param name="threshold" value="Debug"/>
<layout type="log4net.Layout.PatternLayout">
<param value="%d [%t] %-5p %c{2} - %m%n" name="conversionPattern"/>
</layout>
</appender>
<root>
<level value="INFO" />
<appender-ref ref="FileAppender" />
</root>
</log4net>

If you put log4net configuration setting into the app.config or the web.config file the put into the AssemblyInfo.cs file in the Properties folder of your project the following line:
[assembly: log4net.Config.XmlConfigurator(Watch = true)]
Quote from the manual:
// Configure log4net using the .config file
[assembly: log4net.Config.XmlConfigurator(Watch=true)]
// This will cause log4net to look for a configuration file
// called TestApp.exe.config in the application base
// directory (i.e. the directory containing TestApp.exe)
// The config file will be watched for changes.

The assembly attribute must be in the MainApp project, not in the Utilities project.
As it says in the documentation for assembly attributes
Therefore if you use configuration attributes you must invoke log4net
to allow it to read the attributes. A simple call to
LogManager.GetLogger will cause the attributes on the calling assembly
to be read and processed. Therefore it is imperative to make a logging
call as early as possible during the application start-up, and
certainly before any external assemblies have been loaded and invoked.

Not able to get log4net working to write to file

I am using sharpdevelop to create a console application in C#. I have added in the reference for log4net and I added my logging statements while I was writing the code but I never looked at the log file. Now I am done with the code I need to get the log file working. My program runs fine, even the logging statements, but I can't find the log file.
I have tried to cobble together a couple of examples on getting log4net working. I have the lines to read from the configuration and then to instantiate the object, these are the first lines in my program to run:
log4net.Config.XmlConfigurator.Configure();
ILog datalogger = LogManager.GetLogger("myLog"); //initiate the data logger
Then in various places throughout the code I have this:
datalogger.Info(DateTime.Now.ToString() + ": using file: " + ProDirectory.ToString() + #"\" + myProFile.ToString());
I have also put the following in my app.config file:
<appender name="myLogAppender" type="log4net.Appender.RollingFileAppender" >
<file value="myLog.log" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date %level - %message%n" />
</layout>
</appender>
<logger name="myLog">
<level value="All"></level>
<appender-ref ref="myLogAppender" />
</logger>
No matter what I do, I can't see the log file being produced. I have changed the directory and even paused the program to see if I could find a handle open to the log file. Each time I come up empty. Not sure what I could be doing wrong.

not sure if this will help. I also had hard times making log4net work in different scenarios.
I use log4net root xml node to specify the appender. hope it will help.
<log4net>
<appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="log.txt" />
<appendToFile value="true" />
<rollingStyle value="Size" />
<maxSizeRollBackups value="10" />
<maximumFileSize value="250KB" />
<staticLogFileName value="true" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
</layout>
</appender>
<root>
<level value="DEBUG" />
<appender-ref ref="RollingFileAppender" />
</root>
UPDATE
You might also want to check Visual Studio output log. First setup the output log to log "ALL" (somewhere in VS settings). Then you should see exact error message of log4net in the output window of Visual Studio.

Whenever I have had issues with log4net creating the log file, it usually wound up being a file / directory permissions issue.
Change your <file value="log.txt" /> to something that you know will be accessible by the current user / process running devhost.
For example: <file value="%USERPROFILE%\Documents\log.txt" /> will create a log file in the user's My Documents folder. This is a folder that the user has permissions to write data to, and shouldn't give you any troubles with.
For more information on special folder values, see this link.

Looks like I just had to clean up my XML a little, after I did the log file is working fine:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections> <!-- Level 1 -->
<section name="log4net"
type="log4net.Config.Log4NetConfigurationSectionHandler,
log4net"/> <!-- Level 2 -->
</configSections>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0" />
</startup>
<log4net>
<appender name="myLogAppender" type="log4net.Appender.RollingFileAppender" >
<file value="myLog.log" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date %level - %message%n" />
</layout>
</appender>
<logger name="myLog">
<level value="All"></level>
<appender-ref ref="myLogAppender" />
</logger>
</log4net>
</configuration>

Log4net doesn't write to file

I want add new log to file.this is my appender:
<appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="mylogfile.txt"/>
<appendToFile value="true"/>
<rollingStyle value="Size"/>
<maxSizeRollBackups value="5"/>
<maximumFileSize value="10MB"/>
<staticLogFileName value="true"/>
<filter type="log4net.Filter.StringMatchFilter">
<stringToMatch value="test"/>
</filter>
<filter type="log4net.Filter.StringMatchFilter">
<stringToMatch value="error"/>
</filter>
<filter type="log4net.Filter.DenyAllFilter"/>
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %level %logger - %message%newline%exception"/>
</layout>
</appender>
<root>
<level value="All"/>
<appender-ref ref="RollingFileAppender"/>
</root>
and on my class I add
[assembly: XmlConfigurator(Watch = true)]
and I add access everyone for the file but: log4net doesn't write to file. Why?

Log4net fails silently when there's a problem. The design conceit is that no logging is preferable to taking down the application. To figure out what's wrong, turn on Log4net's internal debugging by adding this key to your [app/web].config file:
<appSettings>
<add key="log4net.Internal.Debug" value="true"/>
</appSettings>
The debug messages will be written to the console or to the System.Diagnostics.Trace system. More details from Phill Haack at http://haacked.com/archive/2006/09/26/Log4Net_Troubleshooting.aspx/
There are any number of reasons Log4net might fail. Permissions problems on the log file directory, for starters (especially true for server processes, where your likely running under a restricted set of permissions for security).

You just need to call Configure:
log4net.Config.XmlConfigurator.Configure();
You can see more details here:
Log4net does not write the log file

You need to initialise the logging as the very first step in your app, and from the same assembly that you have the [assembly] tag:
From the docs:
Therefore if you use configuration attributes you must invoke log4net
to allow it to read the attributes. A simple call to
LogManager.GetLogger will cause the attributes on the calling assembly
to be read and processed. Therefore it is imperative to make a logging
call as early as possible during the application start-up, and
certainly before any external assemblies have been loaded and invoked.
Add something like this in your start up code:
LogManager.GetLogger("Initialises logging from assembly attributes");

You should add this config section:
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
</configSections>
to refer the log4net configuration.

log4net log being created but remaining empty

I'm attempting to use log4net. When I fire up the app it creates the log file, but no matter how many times I call Log.Info("Application Started"); it remains empty. I've researched the first two pages that google returns and my code seems to match all examples.
Code:
[assembly: XmlConfigurator(Watch = true)]
namespace Generator
{
public class Run
{
private static readonly log4net.ILog Log =
log4net.LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
public List<BILL_RUN> PerformBillRun()
{
XmlConfigurator.Configure();
Log.Info("Application Started");
var enabled = Log.IsInfoEnabled; //This is true
}
}
}
app.config
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
</configSections>
<log4net>
<appender name="FileAppender" type="log4net.Appender.FileAppender">
<file value="log-files.txt" />
<appendToFile value="true" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
</layout>
</appender>
<root>
<level value="All" />
<appender-ref ref="FileAppender" />
</root>
</log4net>
Any pointers as to what may be wrong?

This always happens to me...as soon as I post the question.
It turns out my <configSections></configSections> tags weren't directly a child to <configuration> meaning that the config wouldn't be picked up (I assume), and because log4net swallows all exceptions this only manifested itself further into my app.
Logging is working fine now.