var numbers = testDS.Tables["Numbers"].AsEnumerable();

                var numberGroups =
                    from n in numbers
                    group n by n.Field<int>("number") % 5 into g
                    select new { Remainder = g.Key, Numbers = g };

                foreach (var g in numberGroups)
                {
                    Console.WriteLine("Numbers with a remainder of {0} when divided by 5:", g.Remainder);
                    foreach (var n in g.Numbers)
                    {
                        Console.WriteLine(n.Field<int>("number"));
                    }
                }