상속: BaseModel
        //creates the standard number of shares for an airline
        public static void CreateStandardAirlineShares(Airline airline, double sharePrice)
        {
            var rnd = new Random();

            const int numberOfShares = 10000;

            int airlinePercentShares = rnd.Next(55, 65);

            airline.Shares = new List<AirlineShare>();

            int airlineShares = (numberOfShares/100)*airlinePercentShares;

            //airline shares
            lock (airline.Shares)
            {
                for (int i = 0; i < airlineShares; i++)
                {
                    var share = new AirlineShare(airline, sharePrice);

                    airline.Shares.Add(share);
                }

                //'free' shares
                for (int i = airlineShares; i < numberOfShares; i++)
                {
                    var share = new AirlineShare(null, sharePrice);

                    airline.Shares.Add(share);
                }
            }
        }
 //adds a number of shares to an airline
 public static void AddAirlineShares(Airline airline, int shares, double sharePrice)
 {
     for (int i = 0; i < shares; i++)
     {
         var share = new AirlineShare(null, sharePrice);
         airline.Shares.Add(share);
     }
 }