private string DeleteBusTicket(string from, string to, string travelCompany, string dateAndTime)
        {
            BusTicket ticket = new BusTicket(from, to, travelCompany, dateAndTime);
            string result = this.DeleteTicket(ticket);

            if (result.Contains(GlobalConstants.Deleted))
            {
                this.busTicketsCount--;
            }

            return result;
        }
        protected string AddBusTicket(string from, string to, string travelCompany, string dateTime, string price)
        {
            BusTicket ticket = new BusTicket(from, to, travelCompany, dateTime, price);
            string key = ticket.DataKey;
            string result;

            if (this.ticketsByDataKey.ContainsKey(key))
            {
                result = GlobalConstants.Duplicated + ticket.Type.ToString().ToLower();
            }
            else
            {
                this.ticketsByDataKey.Add(key, ticket);
                string fromToKey = ticket.FromToKey;

                this.ticketsByFromToKey.Add(fromToKey, ticket);
                this.ticketsByDateAndTime.Add(ticket.DateAndTime, ticket);
                result = ticket.Type + " " + GlobalConstants.Created;
                this.busTicketsCount++;
            }

            return result;
        }