如何使用lambda表达式查询嵌套列表

时间：2023-02-03 18:01:44

In my repository implementation I can run the following query using a lambda expression:

在我的存储库实现中，我可以使用lambda表达式运行以下查询：

public IList<User> GetUsersFromCountry(string)
{
    return _UserRepository.Where(x => x.Country == "Sweden").ToList();                  
}

So far so good, simple stuff. However, I'm having difficulties to write a lambda expression against a nested -> nested list. Given the following example (sorry couldn't think of a better one):

到目前为止，这么好，简单的东西。但是，我很难针对嵌套 - >嵌套列表编写lambda表达式。鉴于以下示例（抱歉无法想到更好的一个）：

The following query works absolutely fine and returns all clubs, which have members over the age of 45

以下查询绝对正常，并返回所有俱乐部，其成员年龄超过45岁

public IList<Clubs> GetGoldMembers()
        {
            var clubs =   from c in ClubRepository
                          from m in c.Memberships 
                          where m.User.Age  >  45
                          select c;

            return clubs;
        }

At the moment, this is where my knowledge of lambda expression ends.

目前，这是我对lambda表达的知识结束的地方。

How could I write the above query against the ClubRepository, using a lambda expression, similar to the example above?

我如何使用lambda表达式对ClubRepository编写上述查询，类似于上面的示例？

2 个解决方案

#1

This might work (untested)...

这可能有用（未经测试）......

var clubs = ClubRepository.Where(c=>c.MemberShips.Any(m=>m.User.Age > 45));

#2

Here's one way to do it:

这是一种方法：

var clubs = clubRepository
    .SelectMany(c => c.Memberships, (c, m) => new { c, m })
    .Where(x => x.m.User.Age > 45)
    .Select(x => x.c);

#1