Fibonacci Interface C#

Class:
        public static IEnumerable<int> Fibonacci()
        {
            int a = 0;
            int b = 1;

            while (true)
            {
                yield return a;
                a += b;
                yield return b;
                b += a;
            }
        }

Example:
    var i = 0;
    foreach (var it in Fibonacci()) {
        Console.WriteLine(it);
        if (++i >= 10) break;
    }