State Design Pattern

Program.cs

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

namespace StatePattern
{
    //state
    public abstract class State
    {
        public BankAccount Account { get; set; }
        public double Balance { get; set; }

        public abstract void Deposit(double amount);
        public abstract void Withdraw(double amount);
    }
    //concrete state
    public class Normal : State
    {
        public Normal(State state)
        {
            Balance = state.Balance;
            Account = state.Account;
        }
        public Normal(double balance, BankAccount account)
        {
            Balance = balance;
            Account = account;
        }
        public override void Deposit(double amount)
        {
            Balance += amount;
            CheckState();
        }

        public override void Withdraw(double amount)
        {
            Balance -= amount;
            CheckState();
        }
        void CheckState()
        {
            if (Balance > 1000)
                Account.State = new Classic(this);
        }
    }
    //concrete state
    public class Classic : State
    {
        public Classic(State state)
        {
            Balance = state.Balance;
            Account = state.Account;
        }
        public Classic(double balance, BankAccount account)
        {
            Balance = balance;
            Account = account;
        }
        public override void Deposit(double amount)
        {
            Balance += amount;
            CheckState();
        }
        public override void Withdraw(double amount)
        {
            Balance -= amount;
            CheckState();
        }
        void CheckState()
        {
            if (Balance < 1000)
                Account.State = new Normal(this);
            else if (Balance > 2000)
                Account.State = new Platinum(this);
        }
    }
    //concrete state
    public class Platinum : State
    {
        public Platinum(State state)
        {
            Balance = state.Balance;
            Account = state.Account;
        }
        public Platinum(double balance, BankAccount account)
        {
            Balance = balance;
            Account = account;
        }
        public override void Deposit(double amount)
        {
            Balance += amount;
            CheckState();
        }
        public override void Withdraw(double amount)
        {
            Balance -= amount;
            CheckState();
        }
        void CheckState()
        {
            if (Balance < 2000)
                Account.State = new Classic(this);
            else if (Balance < 1000)
                Account.State = new Normal(this);
        }
    }
    //context
    public class BankAccount
    {
        public State State { get; set; }
        public string Name { get; set; }
        public BankAccount(string name)
        {
            Name = name;
            State = new Normal(0, this);
        }
        public double Balance
        {
            get { return State.Balance; }
        }
        public void Deposit(double amount)
        {
            State.Deposit(amount);
            Console.WriteLine("Deposited - {0}", amount);
            Console.WriteLine("Balance - {0}", Balance);
            Console.WriteLine("Account Status - {0}", State.GetType().Name);
            Console.WriteLine(new string('-', 50));
        }
        public void Withdraw(double amount)
        {
            State.Withdraw(amount);
            Console.WriteLine("Withdrawn - {0}", amount);
            Console.WriteLine("Balance - {0}", Balance);
            Console.WriteLine("Account Status - {0}", State.GetType().Name);
            Console.WriteLine(new string('-', 50));
        }
    }
    class Program
    {
        //entry point
        static void Main(string[] args)
        {
            BankAccount account = new BankAccount("Mitesh Sureja");
            account.Deposit(500);
            account.Deposit(600);
            account.Deposit(1000);
            account.Withdraw(500);
            account.Withdraw(1500);
            Console.Read();
        }
    }
}