State.cs

namespace DoFactory.GangOfFour.State.RealWorld
{
    /// <summary>
    /// The 'State' abstract class
    /// </summary>
    public abstract class State
    {
        protected Account account;
        protected double balance;
        protected double interest;
        protected double lowerLimit;
        protected double upperLimit;

        // Properties
        public Account Account
        {
            get { return account; }
            set { account = value; }
        }

        public double Balance
        {
            get { return balance; }
            set { balance = value; }
        }

        public abstract void Deposit(double amount);

        public abstract void Withdraw(double amount);

        public abstract void PayInterest();

    }
}