c# - 如何以编程方式更新 log4net 配置文件？

Question

我目前在应用程序的 app.config 文件中有 log4net 配置，如下所示:

...
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
  </configSections>
  <log4net>
    <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="logs\Service.log"/>
      <appendToFile value="true"/>
      <rollingStyle value="Date"/>
      <datePattern value="yyyyMMdd"/>
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger - %message%newline"/>
      </layout>
    </appender>
    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger - %message%newline"/>
      </layout>
    </appender>
    <logger name="Data.WebService">
      <level value="ALL"/>
      <appender-ref ref="ConsoleAppender"/>
      <appender-ref ref="RollingLogFileAppender"/>
    </logger>
    <logger name="Data.Host.HostService">
      <level value="ALL"/>
      <appender-ref ref="ConsoleAppender"/>
      <appender-ref ref="RollingLogFileAppender"/>
    </logger>
  </log4net>

我知道我可以通过 log4net.Config.XmlConfigurator.Configure(); 读取它，但是，我也希望能够通过某种调用来更新它。我将接受来自 Web 服务的配置，一旦我有 set the new config (目前只有日志级别，但我不排除其他可配置的东西)，我需要更新配置文件中的内容。

将所有配置放在一个文件中非常方便，但是，如果这样更简单，我愿意将配置放在另一个文件中。

Answer 1

由于没有官方方法，我最终编写了一个方法，使用 xpath 定位要更改的元素，然后相应地进行更新。对于我需要做的事情来说效果很好，并且比蛮力“readinthefiletoastringthenreplacethetextthensavethestringtothefile”方法更优雅。

    public enum Log4NetConfigItem
    {
        LOGLEVEL
    }

    public const string LOG4NET_CONFIGFILE = "log4net.config";

    public void UpdateConfiguration(Log4NetConfigItem which, object value)
    {
        // Load the config file.
        XmlDocument doc = new XmlDocument();
        doc.Load(LOG4NET_CONFIGFILE);
        // Create an XPath navigator for the document.
        XPathNavigator nav = doc.CreateNavigator();

        try
        {
            XPathExpression expr;

            // Compile the correct XPath expression for the element we want to configure.
            switch (which)
            {
                default:
                case Log4NetConfigItem.LOGLEVEL:
                    // Compile a standard XPath expression
                    expr = nav.Compile("/configuration/log4net/logger/level");
                    break;
            }

            // Locate the node(s) defined by the XPath expression.
            XPathNodeIterator iterator = nav.Select(expr);

            // Iterate on the node set
            while (iterator.MoveNext())
            {
                XPathNavigator nav2 = iterator.Current.Clone();

                // Update the element as required.
                switch (which)
                {
                    default:
                    case Log4NetConfigItem.LOGLEVEL:
                        // Update the 'value' attribute for the log level.
                        SetAttribute(nav2, String.Empty, "value", nav.NamespaceURI, value.ToString());
                        break;
                }
            }

            // Save the modified config file.
            doc.Save(LOG4NET_CONFIGFILE);
        }
        catch (Exception ex) 
        {
            Console.WriteLine(ex.Message);
        }
    }

    void SetAttribute(System.Xml.XPath.XPathNavigator navigator, String prefix, String localName, String namespaceURI, String value)
    {
        if (navigator.CanEdit == true)
        {
            // Check if given localName exist
            if (navigator.MoveToAttribute(localName, namespaceURI))
            {
                // Exist, so set current attribute with new value.
                navigator.SetValue(value);
                // Move navigator back to beginning of node
                navigator.MoveToParent();
            }
            else
            {
                // Does not exist, create the new attribute
                navigator.CreateAttribute(prefix, localName, namespaceURI, value);
            }
        }
    }

注意:我从here得到的SetAttribute代码.