public static void AddDifficultyLevel(DifficultyLevel level)
 {
     _levels.Add(level);
 }
 //removes a difficulty level
 public static void RemoveDifficultyLevel(DifficultyLevel level)
 {
     _levels.Remove(level);
 }
        private void btnCreate_Click(object sender, RoutedEventArgs e)
        {
            var slMoney = UIHelpers.FindChild<Slider>(this, "money");
            var slLoan = UIHelpers.FindChild<Slider>(this, "loan");
            var slPrice = UIHelpers.FindChild<Slider>(this, "price");
            var slPassengers = UIHelpers.FindChild<Slider>(this, "passengers");
            var slAI = UIHelpers.FindChild<Slider>(this, "AI");
            var slStartData = UIHelpers.FindChild<Slider>(this, "startdata");

            double money = slMoney.Value;
            double loan = slLoan.Value;
            double passengers = slPassengers.Value;
            double price = slPrice.Value;
            double AI = slAI.Value;
            double startData = slStartData.Value;

            var level = new DifficultyLevel("Custom", money, loan, passengers, price, AI, startData);

            WPFMessageBoxResult result = WPFMessageBox.Show(
                Translator.GetInstance().GetString("MessageBox", "2406"),
                Translator.GetInstance().GetString("MessageBox", "2406", "message"),
                WPFMessageBoxButtons.YesNo);

            if (result == WPFMessageBoxResult.Yes)
            {
                DifficultyLevels.AddDifficultyLevel(level);

                //PageNavigator.NavigateTo(new PageNewGame());
            }
        }