synchronizing XML nodes between class and file using C#

Question

I'm trying to write an IXmlSerializable class that stays synced with an XML file. The XML file has the following format:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <logging>
    <logLevel>Error</logLevel>
  </logging>
  ...potentially other sections...
</configuration>

I have a DllConfig class for the whole XML file and a LoggingSection class for representing <logging> and its contents, i.e., <logLevel>. DllConfig has this property:

[XmlElement(ElementName = LOGGING_TAG_NAME,
    DataType = "LoggingSection")]
public LoggingSection Logging { get; protected set; }

What I want is for the backing XML file to be updated (i.e., rewritten) when a property is set. I already have DllConfig do this when Logging is set. However, how should I go about doing this when Logging.LogLevel is set? Here's an example of what I mean:

var config = new DllConfig("path_to_backing_file.xml");
config.Logging.LogLevel = LogLevel.Information; // not using Logging setter, but a
                                                // setter on LoggingSection, so how
                                                // does path_to_backing_file.xml
                                                // have its contents updated?

My current solution is to have a SyncedLoggingSection class that inherits from LoggingSection and also takes a DllConfig instance in the constructor. It declares a new LogLevel that, when set, updates the LogLevel in the base class and also uses the given DllConfig to write the entire DllConfig out to the backing XML file. Is this a good technique?

I don't think I can just serialize SyncedLoggingSection by itself to the backing XML file, because not all of the contents will be written, just the <logging> node. Then I'd end up with an XML file containing only the <logging> section with its updated <logLevel>, instead of the entire config file with <logLevel> updated. Hence, I need to pass an instance of DllConfig to SyncedLoggingSection.

It seems almost like I want an event handler, one in DllConfig that would notice when particular properties (i.e., LogLevel) in its properties (i.e., Logging) were set. Is such a thing possible?

Answer 1

Since you are implementing IXmlSerializable yourself, you can make DllConfig.Logging private. Then add a public method on DllConfig to set LogLevel instead of setting Logging.LogLevel directly. That will be the only way you can change the LogLevel. In the implementation of that public method, you can serialize the whole DllConfig to overwrite the xml.