FibonacciKata.cs

FibonacciKata.cs

using System;
using System.Reactive.Linq;


namespace FibonacciKata
{
  
  class Program
  {
    public const int LIMIT = 4000000;
    static void Main(string[] args)
    {      
      Observable.Generate(new
                            {
                              Previous = 1,
                              Current = 2,
                              Total = 0
                            },
                          state => state.Previous <= LIMIT,
                          state => new
                                     {
                                       Previous = state.Current,
                                       Current = state.Previous + state.Current,
                                       Total = state.Total + (state.Current % 2 == 0 ? state.Current : 0)
                                     },                          
                          state => state.Total)                          
                          .TakeLast(1)
                          .Subscribe(Console.WriteLine);

      Console.ReadLine();
    }