Configuration objConfig = ConfigurationManager.OpenExeConfiguration(System.Windows.Forms.Application.StartupPath + @"\TestConfig.exe");

//需要有TestConfig.exe文件
                ConnectionStringsSection objAppsettings = null;
                objAppsettings = (ConnectionStringsSection)objConfig.GetSection("connectionStrings");
                foreach (ConnectionStringSettings s in objAppsettings.ConnectionStrings)
                {
                    Console.WriteLine(s.Name);
                    if (s.Name == "ConnectionString")
                    {
                        string ss;
                        if (s.LockItem == false)
                        {
                            ss = s.ConnectionString;
                            s.ConnectionString += " encrypt";
                            s.LockItem = true;
                            objConfig.Save(ConfigurationSaveMode.Modified);
                        }
                        else
                        {
                            ss = s.ConnectionString;

}
                        Console.WriteLine(ss);
                    }
                }
                Console.ReadKey();

if (!objAppsettings.SectionInformation.IsProtected)
                {
                    objAppsettings.SectionInformation.ProtectSection("RsaProtectedConfigurationProvider");
                    objAppsettings.SectionInformation.ForceSave = true;
                    objConfig.Save(ConfigurationSaveMode.Modified);
                }
                else
                {
                    objAppsettings.SectionInformation.UnprotectSection();
                    objAppsettings.SectionInformation.ForceSave = true;
                    objConfig.Save(ConfigurationSaveMode.Modified);
                }