winform客户端程序实时读写app.config文件

新接到需求，wcf客户端程序运行时，能实时修改程序的打印机名称；

使用XmlHelper读写 winform.exe.config文件修改后始终，不能实时读取出来，查询博客园，原来已有大神解释了；

获取电脑连接的打印机列表需要引入using System.Drawing.Printing;

       #region GetPrinters
        private List<string> GetPrinters()
        {
            var printerNames = new List<string>();
            foreach (var printer in PrinterSettings.InstalledPrinters)
            {
                printerNames.Add(printer.ToString());
            }
            return printerNames;
        }
        #endregion

 指定打印机列表默认显示打印机为配置文件中的打印机：

    printerNames.ForEach(o =>
           {
               if (defaultPrinter == o)
                   cbxPrinterList.SelectedIndex = printerNames.IndexOf(o);
           });

确定按钮修改默认打印机名称

         #region 判断是否有key
            if (ConfigurationManager.AppSettings["DefaultPrinterName"] == null)
            {
                XmlHelper.UpdateKey("DefaultPrinterName", "ZDesigner GT800-300dpi EPL", WMSWinConstant.ApplicatonName + ".exe");
            }
            else
            {
                var printerName = cbxPrinterList.Text;
  
                //string appDomainConfigFile = AppDomain.CurrentDomain.SetupInformation.ConfigurationFile;
                Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                AppSettingsSection appSettings = (AppSettingsSection)config.GetSection("appSettings");
                appSettings.Settings["DefaultPrinterName"].Value = printerName;
                config.Save();
              //重点这句
                ConfigurationManager.RefreshSection("appSettings");
            }
            #endregion        

　获取默认打印机

public  static PrintDocument fPrintDocument = new PrintDocument();

//获取本机默认打印机名称 
public static String DefaultPrinter()
{
return fPrintDocument.PrinterSettings.PrinterName;
}