in the configuration file, not config section is defined, you can use the following code to initialize the configuration.

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
MyConfigSection sec = fred.GetSection("MyConfigSection") as MyConfigSection;
if (sec == null)
  Console.WriteLine("sec is null");
  sec = new MyConfigSection();
  sec.SectionInformation.AllowDefinition = ConfigurationAllowDefinition.MachineToApplication;
  sec.Age = 12;
  config.Sections.Add("mysec", sec);
        Please note that the sec should be also initialized, if there is not, only the Section definiton is defined, but not the actual configuration section.