Yield - Example

gistfile1.cs

public object Solve()
{
    return Fibonnaci().Where(i => i % 2 == 0).Sum();
}

private static IEnumerable<int> Fibonnaci()
{
    int a = 1, b = 2;
    
    yield return a;
    yield return b;

    while (b < 4000000)
    {
        var auxiliar = b;
        b += a;
        a = auxiliar;
 
        yield return b;
    }

}