private Receipt Execution_SendInvoice(Account account, double minutes)
            {
                var price   = _CalculatePrice(account.SpaceShip, minutes);
                var endTime = DateTime.Now.AddMinutes(minutes);
                var receipt = new Receipt
                {
                    Account   = account,
                    Price     = price,
                    StartTime = DateTime.Now.ToString("g"),
                    EndTime   = endTime.ToString("g")
                };

                if (ConnectionString == null)
                {
                    throw new Exception("The static property ConnectionString has not been assigned.",
                                        new Exception(
                                            "Please assign a value to the static property ConnectionString before calling any methods"));
                }
                var dbHandler = new StarWarsContext {
                    ConnectionString = ConnectionString
                };

                dbHandler.Receipts.Update(receipt);
                dbHandler.SaveChanges(); //TODO
                return(receipt);
            }
            public static void ReRegisterShip(Account account, SpaceShip ship)
            {
                ship.SpaceShipID  = account.SpaceShip.SpaceShipID;
                account.SpaceShip = ship;

                var dbHandler = new StarWarsContext {
                    ConnectionString = ConnectionString
                };

                dbHandler.SpaceShips.Update(ship);
                dbHandler.SaveChanges();
            }
            //Async method. Below will call upon a private corresponding method in another thread.
            private void _Register(User inputUser, SpaceShip inputShip, string accountName, string password)
            {
                var dbHandler = new StarWarsContext {
                    ConnectionString = ConnectionString
                };
                var outputAccount = new Account
                {
                    AccountName = accountName,
                    Password    = PasswordHashing.HashPassword(password),
                    User        = inputUser,
                    SpaceShip   = inputShip
                };

                inputUser.Homeplanet = dbHandler.Homeworlds.FirstOrDefault(g => g.Name == inputUser.Homeplanet.Name) ??
                                       inputUser.Homeplanet;
                dbHandler.Accounts.Add(outputAccount);
                dbHandler.SaveChanges();
            }