how set default appender in web config?

Question

i have 2 appender in web config ,first one save logs in xml file , and another save logs using external API , my issue is :

i need to set my default appender is to call external API just , no need to save on xml file , and if api reutred failed , i want to use logging by xml file ( i did it at run time). main question : how to set first appender is default for logging in web.config file

web.config :

<log4net>
     <!--workflow logging-->
    <appender name="LogFileAppender" type="log4net.Appender.RollingFileAppender" >
      <param name="File" value="C:/Workspaces/workflowLog/workflow-info.xml" />
      <param name="AppendToFile" value="true" />
      <rollingStyle value="Size" />
      <maxSizeRollBackups value="10" />
      <maximumFileSize value="10MB" />
      <staticLogFileName value="true" />
      <layout type="Tahaluf.Workflow.Common.Core.Log.WorkFlowXmlLayout" />
    </appender>




    <!--Connect to Tahaluf Logging-->
    <appender name="WorkFlowAppender" type="Tahaluf.Workflow.Common.Core.Log.WorkFlowAppender"> 
    </appender>

    <root>
      <level value="ALL"  />
      <appender-ref ref="WorkFlowAppender"  />
      <appender-ref ref="LogFileAppender" />
    </root>
  </log4net>

Answer 1

Only set your default appender in your web.config. You want to use the WorkFlowAppender, so remove the LogFileAppender.

<root>
  <level value="ALL"/>
  <appender-ref ref="WorkFlowAppender"/>
</root>

If you need to use your LogFileAppender later, you add it by code.

// Add an appender to a logger
public void AddAppender(string loggerName,
log4net.Appender.IAppender appender)
{
  log4net.ILog log = log4net.LogManager.GetLogger(loggerName);
  log4net.Repository.Hierarchy.Logger l =
(log4net.Repository.Hierarchy.Logger)log.Logger;

  l.AddAppender(appender);
}

// Find a named appender already attached to a logger
public log4net.Appender.IAppender FindAppender(string
appenderName)
{
  foreach (log4net.Appender.IAppender appender in
log4net.LogManager.GetRepository().GetAppenders())
  {
    if (appender.Name == appenderName)
    {
      return appender;
    }
  }
  return null;
}

Take a look at this post, too.

Edit This solution doesn't work when the appender-ref of LogFileAppender is not set.

Answer 2

The solution is to modify the Threshold of the appender.

web.config:

<root>
  <level value="ALL"  />
  <appender-ref ref="WorkFlowAppender"  />
  <appender-ref ref="LogFileAppender" />
</root>

Add method:

public static void SetThreshold(string appenderName, log4net.Core.Level threshold)
    {
        foreach (log4net.Appender.AppenderSkeleton appender in log4net.LogManager.GetRepository().GetAppenders())
        {
            if (appender.Name == appenderName)
            {
                appender.Threshold = threshold;
                break;
            }
        }
    }

Turn appender off: SetThreshold("LogFileAppender", log4net.Core.Level.Off);

Turn appender on: SetThreshold("LogFileAppender", log4net.Core.Level.Debug); Level can be any valid level (not only Debug)