本文介绍了区别与选择之间的SelectMany的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我一直在寻找选择
和的SelectMany
,但我一直没能找到之间的差异合适的答案。我需要使用LINQ to SQL时学习差异,但所有我发现是标准排列的例子。
I've been searching the difference between Select
and SelectMany
but I haven't been able to find a suitable answer. I need to learn the difference when using LINQ To SQL but all I've found are standard array examples.
有人可以提供LINQ to SQL的例子吗?
Can someone provide a LINQ To SQL example?
推荐答案
<$c$c>SelectMany$c$c>平坦返回列表的列表查询。例如:
SelectMany
flattens queries that return lists of lists. For example
public class PhoneNumber
{
public string Number { get; set; }
}
public class Person
{
public IEnumerable<PhoneNumber> PhoneNumbers { get; set; }
public string Name { get; set; }
}
IEnumerable<Person> people = new List<Person>();
// Select gets a list of lists of phone numbers
IEnumerable<IEnumerable<PhoneNumber>> phoneLists = people.Select(p => p.PhoneNumbers);
// SelectMany flattens it to just a list of phone numbers.
IEnumerable<PhoneNumber> phoneNumbers = people.SelectMany(p => p.PhoneNumbers);
// And to include data from the parent in the result:
// pass an expression to the second parameter (resultSelector) in the overload:
var directory = people
.SelectMany(p => p.PhoneNumbers,
(parent, child) => new { parent.Name, child.Number });
请参阅SelectMany - StackOverflow的文档
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