![](/Images/OutliningIndicators/ContractedBlock.gif)
![](/Images/OutliningIndicators/ExpandedBlockStart.gif)
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.Settings["sn"].Value = textBox1.Text.Trim().ToUpper();
config.Save(ConfigurationSaveMode.Full);
ConfigurationManager.RefreshSection("appSettings");