See the Framework Support document for more information. Loggers and Appenders Log4net has three main components: loggers, appenders and layouts. These three types of components work together to enable developers to log messages according to message type and level, and to control at runtime how these messages are formatted and where they are reported. These components are helped by filters that control the actions of the appender and object renderers that turn objects into strings. WriteLine resides in its ability to disable certain log statements while allowing others to print unhindered.
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Observation shows that approximately 4 percent of code is dedicated to logging. Consequently, even moderately sized applications will have thousands of logging statements embedded within their code. Given their number, it becomes imperative to manage these log statements without the need to modify them manually. The log4net environment is fully configurable programmatically. However, it is far more flexible to configure log4net using configuration files.
Currently, configuration files are written in XML. Let us give a taste of how this is done with the help of an imaginary application MyApp that uses log4net. Configure ; log. Info "Entering application. DoIt ; log. Info "Exiting application. It then defines a static logger variable with the name MyApp which happens to be the fully qualified name of the class. Debug "Did it again! Configure method creates a rather simple log4net setup. This method is hardwired to add to the root logger a ConsoleAppender.
Note that by default, the root logger is assigned to Level. Bar - Did it again! As a side note, let me mention that in log4net child loggers link only to their existing ancestors. In particular, the logger named Com. Bar is linked directly to the root logger, thereby circumventing the unused Com or Com. Foo loggers. The MyApp class configures log4net by invoking BasicConfigurator. Configure method.
Other classes only need to import the log4net namespace, retrieve the loggers they wish to use, and log away. The previous example always outputs the same log information. Fortunately, it is easy to modify MyApp so that the log output can be controlled at run-time. Here is a slightly modified version. Configure new System. FileInfo args ; log. The path to the configuration file is specified on the command line. Here is a sample configuration file that results in exactly same output as the previous BasicConfigurator based example.
Foo package. The following configuration file shows one possible way of achieving this. As the logger Com. Bar does not have an assigned level, it inherits its level from Com. Foo, which was set to WARN in the configuration file.
The log statement from the Bar. Here is another configuration file that uses multiple appenders. In addition, as the root logger has been allocated a second appender, output will also be directed to the example. This file will be rolled over when it reaches KB. When roll-over occurs, the old version of example. Note that to obtain these different logging behaviors we did not need to recompile code. We could just as easily have logged to an email address, redirected all Com.
Foo output to an NT Event logger, or forwarded logging events to a remote log4net server, which would log according to local server policy.
For more examples of configuring appenders using the XmlConfigurator see the Example Appender Configuration document. Configuration Attributes The log4net configuration can be configured using assembly-level attributes rather than specified programmatically. XmlConfiguratorAttribute The log4net. XmlConfiguratorAttribute Allows the XmlConfigurator to be configured using the following properties: ConfigFile If specified, this is the filename of the configuration file to use with the XmlConfigurator.
This file path is relative to the application base directory AppDomain. This property cannot be used in conjunction with the ConfigFileExtension property.
ConfigFileExtension If specified, this is the extension for the configuration file. The assembly file name is used as the base name with the this extension appended. For example if the assembly is loaded from the a file TestApp. This is equivalent to setting the ConfigFile property to TestApp.
The path to the configuration file is build by using the application base directory AppDomain. BaseDirectory , the assembly file name and the configuration file extension. This property cannot be used in conjunction with the ConfigFile property. Watch If this flag is specified and set to true then the framework will watch the configuration file and will reload the config each time the file is modified.
If neither of the ConfigFile or ConfigFileExtension properties are specified, the application configuration file e. This attribute may only be used once per assembly. However it is worth noting that attributes are purely passive.
They are information only. 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. The setting with the key "log4net. Watch" determines whether the file should be monitored for changes. Even though the assembly attribute [assembly: log4net.
Configuration Files Typically the log4net configuration is specified using a file. This file can be read in one of two ways: Using the. NET System. Configuration API Reading the file contents directly. Because the System. Configuration API does not support reloading of the config file the configuration settings cannot be watched using the log4net. ConfigureAndWatch methods. The main advantage of using the System.
Configuration APIs to read the configuration data is that it requires less permissions than accessing the configuration file directly. The only way to configure an application using the System.
Configuration APIs is to call the log4net. Configure method or the log4net. Configure ILoggerRepository method. In order to embed the configuration data in the.
NET config file parser using a configSections element. The section must specify the log4net. Log4NetConfigurationSectionHandler that will be used to parse the config section. This type must be fully assembly qualified because it is being loaded by the. NET config file parser not by log4net. The correct assembly name for the log4net assembly must be specified. The following is a simple example configuration file that specifies the correct section handler to use for the log4net section.
This assembly must be located where the. NET runtime can find it. For example it could be located in the same directory as the application. If the log4net assembly is stored in the GAC then the fully qualified assembly name must be specified including the culture, version and public key. When using the. The only reason not to read the configuration file directly is if the application does not have sufficient permissions to read the file, then the configuration must be loaded using the.
The file to read the configuration from can be specified using any of the log4net. XmlConfigurator methods that accept a System. FileInfo object.
ALL is a shortcut for all 5 log levels. Debug "This is a debug message" ; log. Info "This is an information message" ; log. Warn "This is a warning message" ; log.
Log4net for .NET Logging: The Only Tutorial and 14 Tips You Need to Know
Global log4net. GlobalContext The global context is shared by all threads in the current AppDomain. This context is thread safe for use by multiple threads concurrently. Thread The thread context is visible only to the current managed thread. Logical Thread log4net. ThreadLogicalContext The logical thread context is visible to a logical thread.
log4net Tutorial - The Complete Guide for beginners and pros
When I have been doing some profiling sessions in the past to optimize code, I have noticed that the constructors on the LogManager object can use a lot of CPU. GetLogger System. DeclaringType ; 2. To help resolve these issues, enable internal log4net logging via your web.