Can ConfigurationManager retain XML comments on Save()?

Question

I've written a small utility that allows me to change a simple AppSetting for another application's App.config file, and then save the changes:

 //save a backup copy first.
 var cfg = ConfigurationManager.OpenExeConfiguration(pathToExeFile);
 cfg.SaveAs(cfg.FilePath + "." + DateTime.Now.ToFileTime() + ".bak"); 

 //reopen the original config again and update it.
 cfg = ConfigurationManager.OpenExeConfiguration(pathToExeFile);
 var setting = cfg.AppSettings.Settings[keyName];
 setting.Value = newValue;

 //save the changed configuration.
 cfg.Save(ConfigurationSaveMode.Full);

This works well, except for one side effect. The newly saved .config file loses all the original XML comments, but only within the AppSettings area. Is it possible to to retain XML comments from the original configuration file AppSettings area?

Here's a pastebin of the full source if you'd like to quickly compile and run it.

Answer 1

If comments are critical, it might just be that your only option is to read & save the file manually (via XmlDocument or the new Linq-related API). If however those comments are not critical, I would either let them go or maybe consider embedding them as (albeit redundant) data elements.

Answer 2

I jumped into Reflector.Net and looked at the decompiled source for this class. The short answer is no, it will not retain the comments. The way Microsoft wrote the class is to generate an XML document from the properties on the configuration class. Since the comments don't show up in the configuration class, they don't make it back into the XML.

And what makes this worse is that Microsoft sealed all of these classes so you can't derive a new class and insert your own implementation. Your only option is to move the comments outside of the AppSettings section or use XmlDocument or XDocument classes to parse the config files instead.

Sorry. This is an edge case that Microsoft just didn't plan for.