using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Please enter the starting value of your gift card:");

        var cardValue = double.Parse(Console.ReadLine());

        var gCard = new GiftCard(cardValue);

        Console.WriteLine("Would you like to enter a transaction?");

        while (Console.ReadLine().ToLower() == "y" || Console.ReadLine().ToLower() == "yes")

        {

            Console.WriteLine("Please enter the amount of the transaction");

            var transaction = double.Parse(Console.ReadLine());

            gCard.UpdateValue(transaction);

            Console.WriteLine("Your new gift card balance is: " + gCard.CurrentValue);

            Console.WriteLine("Would you like to enter another transaction?");

        }

        Console.WriteLine("Thank you for playing");

    }

}

​

internal class GiftCard

{

    public double StartValue {get; private set;}

    public double CurrentValue {get; private set;}

    public static List<double> Transactions = new List<double>();

    public GiftCard(double startValue)

    {

        StartValue = startValue;

        CurrentValue = startValue;

    }

    public void UpdateValue (double transaction)

    {

        CurrentValue -= transaction;

        Transactions.Add(transaction);

    }

}