Question

我有两个班级：

class Person 
{
    public int PersonId { get; set; }
    public string Name { get; set; }  
}
class Phone
{
    public int PersonId { get; set; }
    public string Number { get; set; }
}

两个系列：

List<Person> Persons;
List<Phone> Phones;

我想使用linq加入他们并获取Result对象的结果列表：

class Result
{
    public string Name { get; set; }
    public List<string> Numbers { get; set; }
}

如何在linq中实现这个？

Answer 1

var resultList = 
from person in Persons
select new Result
{
    Name = person.Name,
    Numbers = 
    (
        from phone in Phones 
        where phone.PersonId == person.PersonId 
        select phone.Number
    ).ToList()
}

Answer 2

您可以使用Linq的连接功能

var joinedList = from c in Persons
                 join p in Phones p on p.PersonId equals c.PersonId
                 select new {Persons = c, Phones = p};

更新：

似乎必须将其作为结果返回。我们走了。

var results = Persons.Select(c => new Result
              {
                  Name = c.Name, 
                  Numbers = Phones.Where(p=>p.PersonId == c.PersonId)
                                  .Select(n=>n.Number).ToList()
              });

Answer 3

假设所有电话号码都指向一个现有的人，这将起作用：

var results = Phones.GroupBy(p => p.PersonId)
                    .Select(g => new Result()
{
    Name = Persons.Single(x => x.PersonId == g.Key).Name,
    Numbers = g.Select(x => x.Number).ToList()
});

Answer 4

非常类似迈克......

var resultList = from person in persons
select new Result
{
    Name = person.Name, 
    Numbers = phones
        .Where(x => x.PersonId == person.PersonId)
        .Select(x => x.Number)
        .ToList()
};

Answer 5

纯Method Syntax：

List<Person> people = new List<Person>();   /*Populate the list however you wish*/
List<Phone> phones = new List<Phone>();     /*Populate the list however you wish*/

List<Result> results = people
    .Select(singlePerson => new Result 
    { 
        Name = singlePerson.Name, 
        Numbers = phones
            .Where(singlePhone => singlePhone.PersonId.Equals(singlePerson.PersonId))
            .Select(singlePhone => singlePhone.Number)
            .ToList() 
    })
    .ToList();

Answer 6

好吧，我不会只是通过向人们添加电话项目来加入这两个系列。根据你想要实现的目标，我会使用一个接口来指定这两个类有一些共同点。

但其他解决方案也可以运行，根据您的问题，它可能不是正确的解决方案。

列出作为linq查询结果的属性

6 个答案: