Change appconfig on runtime

Question

I am trying to update the appconfig file on run time with the following code. I do not get an error but it does not update my config file.

System.Configuration.Configuration config =
    ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
string oldValue = config.AppSettings.Settings["Username"].Value;
config.AppSettings.Settings["Username"].Value = "NewValue";
config.Save(ConfigurationSaveMode.Modified);
ConfigurationManager.RefreshSection("appSettings");

Answer 1

Adding the config.AppSettings.SectionInformation.ForceSave = true; will do the trick. You should then look in YourProject.vshost.exe.config when debugging as Justin said. The modifications are saved there.