// Get the current configuration file.
Configuration config = WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

// Get the section.
ConfigurationSection appSec = config.GetSection("appSettings");

if (appSec != null && !appSec.SectionInformation.IsProtected)
 {
     // Protect (encrypt)the section.
    appSec.SectionInformation.ProtectSection("DataProtectionConfigurationProvider");

     // Save the encrypted section.
    appSec.SectionInformation.ForceSave = true;
     config.Save();
 }

Configuration config = WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

 ConfigurationSection section = config.GetSection("appSettings");

if (section != null && section.SectionInformation.IsProtected)
 {
     section.SectionInformation.UnprotectSection();
     config.Save();
 }