Linq Take，但取决于元素的总和(或总计) [英] Linq TakeWhile depending on sum (or aggregate) of elements

问题描述

我有一个元素列表，并希望在总和(或元素的任何集合)满足一定条件的同时进行.下面的代码可以完成这项工作，但是我很确定这不是一个应该存在适当模式的异常问题.

I have a list of elements and want to takeWhile the sum (or any aggregation of the elements) satisfy a certain condition. The following code does the job, but i am pretty sure this is not an unusual problem for which a proper pattern should exist.

var list = new List<int> { 1, 2, 3, 4, 5, 6, 7 };
int tmp = 0;
var listWithSum = from x in list
                  let sum = tmp+=x
                  select new {x, sum};
int MAX = 10;
var result = from x in listWithSum
             where x.sum < MAX
             select x.x;

有人知道如何更好地解决任务，可能将TakeWhile和Aggregate组合成一个查询吗?

Does somebody know how to solve the task in nicer way, probably combining TakeWhile and Aggregate into one query?

Thx

推荐答案

在我看来，您需要类似Scan 方法之类的东西.com/en-us/devlabs/ee794896.aspx"rel =" nofollow noreferrer>反应性扩展(System.Interactive部分)-类似于 Aggregate ，但产生的是序列而不是一个结果.然后，您可以这样做:

It seems to me that you want something like the Scan method from Reactive Extensions (the System.Interactive part) - it's like Aggregate, but yields a sequence instead of a single result. You could then do:

var listWithSum = list.Scan(new { Value = 0, Sum = 0 },
         (current, next) => new { Value = next,
                                  Sum = current.Sum + next });

var result = listWithSum.TakeWhile(x => x.Sum < MaxTotal)
                        .Select(x => x.Value);

( =" MoreLINQ 具有

(MoreLINQ has a similar operator, btw - but currently it doesn't support the idea of the accumulator and input sequence not being the same type.)

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