FizzBuzz.cs

        static void FizzBuzz(int number)
        {
            // 3 MOD 3 = 0. We actually want 1 for multiples of 3.
            // So we store an incremented number so that we get 1
            // for the binary operations. This applies to 5 as
            // well.

            // Valid numbers for X MOD 3 are { 0, 1, 2 }. Therefore
            // we can simply AND it with 1. As such:
            // { 0, 1, 2 } AND 1 =
            // { 0, 1, 0 }

            // Valid numbers for X MOD 5 are { 0, 1, 2, 3, 4 }. If we
            // simply AND it with 1 we will get a false positive on 3.
            // To avoid that we use MOD 3 to 'make' the 3 case 0.
            // Unfortunately that will make the 4 case 1 as the
            // sequence is now { 0, 1, 2, 0, 1 }. To avoid that we
            // MOD it with 4 first. Finally we shift it left one bit
            // to multiply it by 2. As such:
            // { 0, 1, 2, 3, 4 } MOD 4 =
            // { 0, 1, 2, 3, 0 } MOD 3 =
            // { 0, 1, 2, 0, 0 } AND 1 =
            // { 0, 1, 0, 0, 0 } SHL 1 =
            // { 0, 2, 0, 0, 0 }

            byte current = 0;
            int inc = number + 1;

            // 3 case.
            current |= (byte)((inc % 3) & 1);
            // 5 case.
            current |= (byte)(((((inc % 5) % 4) % 3) & 1) << 1);

            switch (current)
            {
                case 1:
                    Console.WriteLine("Fizz");
                    break;
                case 2:
                    Console.WriteLine("Buzz");
                    break;
                case 3: // 1 OR 2 = 3
                    Console.WriteLine("FizzBuzz");
                    break;
                default:
                    Console.WriteLine(number);
                    break;
            }
        }