euler/Program.cs

using System;
using System.Collections.Generic;

namespace Euler {

  class Program {

  	static int Problem1() {
  		int sum = 0;
  		for (int i = 1; i < 1000; i++) {
  			if (i % 3 == 0 || i % 5 == 0) {
  				sum += i;
  			}
  		}
  		return sum;
  	}

  	static long Problem2() {
  		int max = 4_000_000;

  		var fibs = new List<int>();
  		fibs.Add(1);
  		fibs.Add(2);

  		while (fibs[fibs.Count - 1] < max) {
  			int num = fibs[fibs.Count - 1] + fibs[fibs.Count - 2];
 			  fibs.Add(num);
  		}

      int sum = 0;
  		foreach (int i in fibs) {
  			if (i % 2 == 0 && i <= max) {
  				sum += i;
  			}
  		}

  		return sum;
  	}

    static void Main(string[] args) {
      Console.WriteLine(Problem2());
    }
  }
}