public static UpdaterCourse GetInstance()
        {
            if (update == null)
            {
                update = new UpdaterCourse();
            }

            return(update);
        }
        private static void UpdateCourses()
        {
            try
            {
                var m_interval = 0;
                int.TryParse(ConfigurationSettings.AppSettings[UPDATE_INTERVAL_KEY_NAME] ?? UPDATE_INTERVAL, out m_interval);

                while (enableUpdate)
                {
                    UpdaterCourse.GetInstance().Update();
                    Thread.Sleep(m_interval);
                }
            }
            catch (System.Exception ex)
            {
                EventLog.WriteEntry(APPLICATION_LOG,
                                    $"An error occurred in the service 'CurrencyExhcangeService': {ex.Message.ToString()}",
                                    EventLogEntryType.Error);
            }
        }