Yes. As you noticed, the class ConfigurationManagerallows you to read and write configuration files.
ConfigurationManager Class
Scroll down a bit.
Of course, you can read / write these files as XML files, but the above class provides a convenient interface for managing configuration files.
ConfigurationManager, , [ab?] ExeConfigurationFileMap. , file , , Save()
ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap
{
ExeConfigFilename = file
};
var config = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None);
config.Save();