.net dynamically refresh app.config

Question

How do I dynamically reload the app.config in a .net Windows application? I need to turn logging on and off dynamically and not just based upon the value at application sta

Answer 1

I wrote this implementation to change the log level at runtime and persist the new treshold back to the app.config (actually the Application.exe.config).

The interface:

internal interface ILoggingConfiguration
{
  void SetLogLevel(string level);

  string GetLogLevel();
}

The implementation:

internal sealed class LoggingConfigurationImpl : ILoggingConfiguration
{
  #region Members

  private static readonly ILog _logger = 
    ObjectManager.Common.Logger.GetLogger();
  private const string DEFAULT_NAME_SPACE = "Default.Name.Space";

  #endregion

  #region Implementation of ILoggingConfiguration

  public void SetLogLevel(string level)
  {
    Level threshold = Log4NetUtils.ConvertToLevel(level);
    ILoggerRepository[] repositories = LogManager.GetAllRepositories();

    foreach (ILoggerRepository repository in repositories)
    {
      try
      {
        SetLogLevelOnRepository(repository, threshold);
      }
      catch (Exception ex)
      {
        _logger.ErrorFormat("Exception while changing log-level: {0}", ex);
      }
    }
    PersistLogLevel(level);
  }

  public string GetLogLevel()
  {
    ILoggerRepository repository = LogManager.GetRepository();
    Hierarchy hierarchy = (Hierarchy) repository;
    ILogger logger = hierarchy.GetLogger(DEFAULT_NAME_SPACE);
    return ((Logger) logger).Level.DisplayName;
  }

  private void SetLogLevelOnRepository(ILoggerRepository repository,
                                       Level threshold)
  {
    repository.Threshold = threshold;
    Hierarchy hierarchy = (Hierarchy)repository;
    ILogger[] loggers = hierarchy.GetCurrentLoggers();
    foreach (ILogger logger in loggers)
    {
      try
      {
        SetLogLevelOnLogger(threshold, logger);
      }
      catch (Exception ex)
      {
        _logger.ErrorFormat("Exception while changing log-level for 
            logger: {0}{1}{2}", logger, Environment.NewLine, ex);
      }
    }
  }

  private void SetLogLevelOnLogger(Level threshold, ILogger logger)
  {
    ((Logger)logger).Level = threshold;
  }

  private void PersistLogLevel(string level)
  {
    XmlDocument config = new XmlDocument();
    config.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
    string xpath =
      String.Format("configuration/log4net/logger[@name='{0}']/level",
        DEFAULT_NAME_SPACE);
    XmlNode rootLoggerNode = config.SelectSingleNode(xpath);

    try
    {
      rootLoggerNode.Attributes["value"].Value = level;
      config.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);

      ConfigurationManager.RefreshSection("log4net");
    }
    catch(Exception ex)
    {
      _logger.ErrorFormat("error while persisting new log-level: {0}", ex);
    }
  }

  #endregion
}

The helper class Log4NetUtils:

public sealed class Log4NetUtils
{
  private static readonly ILoggerRepository _loggerRepository =
     LoggerManager.GetAllRepositories().First();

  public static Level ConvertToLevel(string level)
  {
    return _loggerRepository.LevelMap[level];
  }
}

The XAML code:

  
  
  
  


            Change log level