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?
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?
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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