这段话能不能用linq搞定？
循环的话，需要一个变量存“总数”。。能用linq改写吗

            List<entity> s = getEntities();  //entity有id字段和qty字段

            //想得到一个新集合，元素个数与旧集合一样，新集合有total和id字段，total字段记录旧集合中前n项的qty字段的和
            var lst = new List<object>();
            decimal totalQty = 0;
            foreach (var t in s)
            {
                totalQty += t.qty;
                lst.Add(new {total = totalQty, id = t.id});
            }

            foreach (var item in lst)
            {
                ...
            }

[解决办法]
给本人的解决方案，两行代码搞定

var query = Enumerable.Range(0, s.Count).Select(x => new { total = s.Select((y, i) => new { y, i }).Where(y => y.i <= x).ToList().Select(y => y.y.qty).ToList().Sum(), id = s.ElementAt(x).id }).ToList();
query.ForEach(item=>Console.WriteLine(item.total+" "+item.id));

[解决办法]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Test 
 
    {
        public int ID { get; set; }
        public int QTY { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var data = new List<Test>() 
            { 
                new Test() { ID = 1, QTY = 3 },
                new Test() { ID = 2, QTY = 1 },
                new Test() { ID = 3, QTY = 4 },
                new Test() { ID = 4, QTY = 2 },
                new Test() { ID = 5, QTY = 2 },
                new Test() { ID = 6, QTY = 5 }
            };
            var query = data.Aggregate(new { total = 0, list = new List<Tuple<int, int>>() },
                (a, x) =>
                {
                    a.list.Add(new Tuple<int, int>(x.ID, x.QTY + a.total));
                    return new { total = x.QTY + a.total, list = a.list };
                }).list.Select(x => new { total = x.Item2, id = x.Item1 });
            foreach (var item in query) 
 
            {
                Console.WriteLine(item.id + ", " + item.total);
            }
        }
    }
}

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