designPattern/DesignPattern/State-VendingMachineExample/DispenseItemState.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace State_VendingMachineExample
{
    internal class DispenseItemState : VMState
    {
        public DispenseItemState(VendingMachine context)
        {
            vendingMachine = context;
        }

        public override void AddMoney(decimal money)
        {
            throw new ApplicationException();
        }

        public override void ReturnChange(decimal money)
        {
            throw new ApplicationException();
        }

        public override void SelectItem(int itemId)
        {
            decimal? price = vendingMachine.GetPrice(itemId).Value;

            // Dispense item here
            Console.WriteLine($"Dispense Item#{itemId} ({price.Value})");

            vendingMachine.Money -= price.Value;

            vendingMachine.State = vendingMachine.DispenseChangeState;
            vendingMachine.State.ReturnChange(vendingMachine.Money);
        }
    }
}