linq partition by

static void Main(string[] args)
        {
            var beatles = (new[] { new { id=1 , inst = "guitar" , name="john" },
new { id=2 , inst = "guitar" , name="george" },
new { id=3 , inst = "guitar" , name="paul" },
new { id=4 , inst = "drums" , name="ringo" },
new { id=5 , inst = "drums" , name="pete" }
});

            //方法1
            //方法2

            foreach (var i in o)
            {
                Console.WriteLine("{0} {1} {2}", i.inst, i.name, i.rn);
            }

            Console.ReadLine();
        }

方法1：

var o = beatles.OrderBy(m => m.id).ToList().GroupBy(x => x.inst)
                .SelectMany(t => t.Select((b, i) => new { b, i })).Select(m => m.b);

方法2：

var o = beatles.OrderBy(x => x.id).GroupBy(x => x.inst)
            .Select(g => new { g, count = g.Count() })
            .SelectMany(t => t.g.Select(b => b).Zip(Enumerable.Range(1, t.count), (j, i) => new { j.inst, j.name, rn = i }));

结果：

guitar john 1 
guitar george 2 
guitar paul 3 
drums ringo 1 
drums pete 2