c# - Select 和 SelectMany 的区别

我一直在寻找 Select 和 SelectMany 之间的区别，但一直找不到合适的答案。我需要了解使用 LINQ To SQL 时的区别，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？

最佳答案

SelectMany 扁平化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 });

Live Demo on .NET Fiddle

关于c# - Select 和 SelectMany 的区别，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/958949/