gistfile1.cs

        public static IEnumerable<int> Div(this int numerator, int denominator)
        {
            //return denominator == 0
            //    ? Enumerable.Empty<int>()
            //    : new[] { numerator/denominator };
            if (denominator != 0) yield return numerator/denominator;
        }

        public static IEnumerable<int> DoSomeDivision(int denominator)
        {
            return from a in 12.Div(denominator)
                   from b in a.Div(2)
                   select b;
        }
...
            var result = 
                from a in new[] { "Hello World!" }
                from b in DoSomeDivision(2)
                from c in new[] { new DateTime(2010, 1, 14) }
                select (a + " " + b.ToString() + " " + c.ToShortDateString());
            Console.WriteLine(result.Any() ? result.First() : "Nothing");