log4net initialisation

问题

I've looked hard for duplicates but have to ask the following, no matter how basic it may seem, to get it clear once and for all!

In a fresh Console app using log4net version 1.2.10.0 on VS28KSP1 on 64 bit W7, I have the following code:-

using log4net;
using log4net.Config;

namespace ConsoleApplication1
{
    class Program
    {
        static readonly ILog _log = LogManager.GetLogger(typeof(Program));
        static void Main(string[] args)
        {
            _log.Info("Ran");
        }
    }
}

In my app.config, I have:

<?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">
      <file value="Program.log" />
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <appendToFile value="true" />
      <rollingStyle value="Size" />
      <maxSizeRollBackups value="10" />
      <maximumFileSize value="1MB" />
      <staticLogFileName value="true" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="[%username] %date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
    </appender>

    <root>
      <level value="DEBUG" />
      <appender-ref ref="RollingFileAppender" />
    </root>
  </log4net>

</configuration>

This doesnt write anything, unless I either add an attribute:

[ assembly:XmlConfigurator ]

Or explicitly initialise it in Main():

_log.Info("This will not go to the log");
XmlConfigurator.Configure();
_log.Info("Ran");

This raises the following questions:

1. I'm almost certain I've seen it working somewhere on some version of log4net without the addition of the assembly attribute or call in Main. Can someone assure me I'm not imagining that?
2. Can someone please point me to where in the doc it explicitly states that both the config section and the initialisation hook are required - hopefully with an explanation of when this changed, if it did?

I can easily imagine why this might be the policy -- having the initialisation step explicit to avoid surprises etc., it's just that I seem to recall this not always being the case... (And normally I have the config in a separate file, which generally takes configsections out of the picture)

回答1:

According to the configuration page in the manual:

The log4net configuration can be configured using assembly-level attributes rather than specified programmatically.

XmlConfiguratorAttribute: The log4net.Config.XmlConfiguratorAttribute Allows the XmlConfigurator to be configured using the following properties:

• ConfigFile ...
• ConfigFileExtension ...

If neither of the ConfigFile or ConfigFileExtension properties are specified, the application configuration file (e.g. TestApp.exe.config) will be used as the log4net configuration file.

Example usage:

// 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.

I agree that it's a bit ambiguous, but I interpret the existence of the example usage to mean that log4net will not use the .config file without the above attribute; and the fact that they point out that you have to use one of the two properties, but do not say anything about leaving out the attribute altogether, suggests to me that the attribute (or programmatic call) is required to use app.config in the way you want.

来源：https://stackoverflow.com/questions/1261158/log4net-initialisation