Select和SelectMany之间的区别

  • Z时代
  • 2024-01-10
  • 分类：问答

我一直在寻找和之间的区别Select，SelectMany但找不到合适的答案。我需要学习使用LINQ To

SQL的区别，但我发现的只是标准数组示例。

有人可以提供LINQ To SQL示例吗？

回答：

SelectMany展平返回列表列表的查询。例如

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 });

.NET Fiddle上的实时演示

以上是 Select和SelectMany之间的区别 的全部内容， 来源链接： utcz.com/qa/423569.html

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