Reactive Extensions Zip FizzBuzz

RxZipFizzBuzz.cs

using System;
using System.Linq;
using System.Reactive.Linq;

namespace RxZipFizzBuzz
{
    class Program
    {
        static void Main(string[] args)
        {
            var numberObserver = Observable.Range(1, 30);
            var no = numberObserver.Select(i => i % 3 != 0 && i % 5 != 0 ? i.ToString() : "");
            var fo = new[] { "", "", "FIZZ" }.ToObservable().Repeat(10);
            var bo = new[] { "", "", "", "", "BUZZ" }.ToObservable().Repeat(6);

            Observable.Zip(no, fo, bo).Subscribe(x => Console.WriteLine( $"{x[0]}{x[1]}{x[2]}"));
            Console.ReadKey();
        }
    }
}

result

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
Fizz
19
Buzz
Fizz
22
23
Fizz
Buzz
26
Fizz
28
29
FizzBuzz