If-Else State Machine

IsElseStateMachine.cs

/*
 * INTRO
 * - Review a classic If/Else implementation
 * - The myth of reducing cyclomatic complexity
 */

using System;

class Program
{
    static void Main(string[] args)
    {
        var combinationLock = new CombinationLock();
        combinationLock.Start();
        Console.WriteLine(string.Format("Starting State: {0}", combinationLock.CurrentState));

        combinationLock.EnterNumber(7);
        Console.WriteLine(combinationLock.CurrentState);

        combinationLock.EnterNumber(1);
        Console.WriteLine(combinationLock.CurrentState);

        combinationLock.EnterNumber(3);
        Console.WriteLine(combinationLock.CurrentState);

        Console.WriteLine(string.Format("Ending State: {0}", combinationLock.CurrentState));
    }
}

public enum CombinationLockState
{
    NoneRight,
    OneRight,
    TwoRight,
    Open
}

public class CombinationLock
{
    public CombinationLockState CurrentState { get; private set; }

    public void EnterNumber(int number)
    {
        var nextState = this.CurrentState;

        if (this.CurrentState == CombinationLockState.NoneRight)
        {
            if (number == 7)
            {
                nextState = CombinationLockState.OneRight;
            }
        }
        else if (this.CurrentState == CombinationLockState.OneRight)
        {
            if (number == 1)
            {
                nextState = CombinationLockState.TwoRight;
            }
            else
            {
                nextState = CombinationLockState.NoneRight;
            }
        }
        else if (this.CurrentState == CombinationLockState.TwoRight)
        {
            if (number == 3)
            {
                nextState = CombinationLockState.Open;
            }
            else
            {
                nextState = CombinationLockState.NoneRight;
            }
        }
        else if (this.CurrentState == CombinationLockState.Open)
        {
            nextState = CombinationLockState.NoneRight;
        }

        this.CurrentState = nextState;
    }

    public void Start()
    {
        this.CurrentState = CombinationLockState.NoneRight;
    }
}