public string GetDestinations()
        {
            DataAbstractionLayer dal = new DataAbstractionLayer();

            if (Request.Params.AllKeys.Contains("DestinationID"))
            {
                bool isValidId = Int32.TryParse(Request.Params["DestinationID"], out int destinationID);
                if (isValidId)
                {
                    Destination destination = dal.GetDestinationById(destinationID);
                    if (destination != null)
                    {
                        return(DestinationToHtml(destination));
                    }
                    return("<h3>No destination with the given ID...</h3>");
                }
                return("<h3>Destination ID is not valid!</h3>");
            }
            List <Destination> destinations = dal.GetDestinations();

            return(DestinationsToTable(destinations));
        }