问ConfigurationManager.RefreshSection("AppSettings")不工作

EN

_envName = System.Environment.GetEnvironmentVariable("ENV");
if (_envName == null)
    throw new Exception ("The ENV environemnt variable must be set");

string envFileName = "app." + _envName.ToLower() + ".config";

System.Configuration.Configuration config = 
     ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.File = envFileName;

config.Save(ConfigurationSaveMode.Full);
ConfigurationManager.RefreshSection("AppSettings");