//lazy construction of instance
        public static DatasourceHandler GetInstance()
        {
            if (_uniqueInstance == null)
            {
                _uniqueInstance = new DatasourceHandler();
            }

            return(_uniqueInstance);
        }
 public static DatasourceHandler GetInstance(Datasource datasource)
 {
     if (_uniqueInstance == null)
     {
         _uniqueInstance = new DatasourceHandler(datasource);
     }
     _datasource = datasource;
     _datasource.LoadPeriods();
     return(_uniqueInstance);
 }