/// <summary>
    /// <example>
    /// public class SecuredController : Controller
    //  {
    //    [AuthorizeFromConfiguration(AppSettingRolesKey = "Roles")]
    //    in config file add: <add key="Authorization.Roles" value="Role1,Role2"/>
    //    public ActionResult Index()
    //    {
    //        return View();
    //    }
    //    [AuthorizeFromConfiguration(AppSettingUsersKey = "Users")]
    //    in config file add: <add key="Authorization.Users" value="domain\user1,domain\user2"/>
    //    public ActionResult Index()
    //    {
    //        return View();
    //    }
    //  }
    //</example>
    /// </summary>
public class AuthorizeFromConfigurationAttribute : AuthorizeAttribute
    {
        public const string ConfigurationKeyPrefix = "Authorization.";
        private string _appSettingRoleKey;
        private string _appSettingUsersKey;

        public string AppSettingRolesKey
        {
            get { return _appSettingRoleKey; }
            set
            {
                if (!string.IsNullOrWhiteSpace(value))
                {
                    _appSettingRoleKey = value;
                    string roles = GetAppSettingValue(_appSettingRoleKey);
                    if (!string.IsNullOrWhiteSpace(roles))
                        Roles = roles;
                }
            }
        }

        private static string GetAppSettingValue(string key)
        {
            if (string.IsNullOrWhiteSpace(key))
            {
                throw new ArgumentNullException("key");
            }
            if (key.IndexOf(ConfigurationKeyPrefix,StringComparison.OrdinalIgnoreCase) < 0)
            {
                key = string.Format("{0}{1}", ConfigurationKeyPrefix, key);
            }

            string keyValue = string.Empty;
            if (ConfigurationManager.AppSettings.AllKeys.Contains(key))
            {
                keyValue = ConfigurationManager.AppSettings[key];
            }
            else
            {
                throw new Exception(string.Format("The key \"{0}\" has not been defined in the configuration file", key));
            }
            return keyValue;
        }

        public string AppSettingUsersKey
        {
            get { return _appSettingUsersKey; }
            set
            {
                if (!string.IsNullOrWhiteSpace(value))
                {
                    _appSettingUsersKey = value;
                    string users = GetAppSettingValue(_appSettingUsersKey);
                    if (!string.IsNullOrWhiteSpace(users))
                        Users = users;
                }
            }
        }
    }