designPattern/DesignPattern/State-VendingMachineExample/VendingMachine.cs

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

namespace State_VendingMachineExample
{
    // Context
    internal class VendingMachine
    {
        private Product product = new Product();
        internal decimal Money { get; set; }

        internal VMState State { get; set; }

        internal VMState ReadyState { get; private set; } 
        internal VMState HasMoneyState { get; private set; } 
        internal VMState DispenseItemState { get; private set; } 
        internal VMState DispenseChangeState { get; private set; } 

        public VendingMachine()
        {
            this.Money = 0;
            this.ReadyState = new ReadyState(this);
            this.HasMoneyState = new HasMoneyState(this);
            this.DispenseItemState = new DispenseItemState(this);
            this.DispenseChangeState = new DispenseChangeState(this);
            this.State = this.ReadyState;
        }

        public void AddMoney(decimal money)
        {
            this.State.AddMoney(money);
        }

        public void SelectItem(int itemId)
        {
            this.State.SelectItem(itemId);
        }

        internal decimal? GetPrice(int itemId)
        {
            return product.GetPrice(itemId);
        }
    }
}