使用Linq在集合中指定元素之后查找元素 [英] Using Linq to find the element after a specified element in a collection

问题描述

我有一份人的有序列表.我有一个我认识的人存在于该收藏集中.如何确定列表中的下一个是谁?

解决方案

您可以执行以下操作:

IEnumerable<Person> persons = ..

var firstPersonAfterJack = persons.SkipWhile(p => p.Name != "Jack")
                                  .ElementAt(1); //Zero-indexed, means second

这个想法是产生一个序列，该序列会导致元素跳过直到满足条件为止，然后获取该序列中的第二个元素.

如果不能保证查询将返回结果(例如，从未找到匹配项，或者该序列的最后一个元素)，则可以将ElementAt替换为ElementAtOrDefault，然后执行null测试以检查成功/失败.

我注意到您在问题中说，您有一个订购的名单.如果您可以更详细地解释这意味着什么，我们也许可以提供更好的答案(例如，我们可能不必线性搜索序列).

I have an ordered list of People. I have a person that I know exists in that collection. How can I determine which person is next in the list?

解决方案

You could do something like this:

IEnumerable<Person> persons = ..

var firstPersonAfterJack = persons.SkipWhile(p => p.Name != "Jack")
                                  .ElementAt(1); //Zero-indexed, means second

The idea is to produce a sequence resulting in skipping elements until you meet the condition, then take the second element of that sequence.

If there's no guarantee that the query will return a result (e.g. a match is never found, or is the last element of the sequence), you could replace ElementAt with ElementAtOrDefault, and then do a null-test to check for success / failure.

I notice you say in your question that you have an ordered list of people. If you could explain what that means in more detail, we might be able to provide a better answer (for example, we may not have to linear-search the sequence).

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