Question

如何根据应用的子对象过滤器过滤父对象集合？

下面是我正在搜索具有 searchClientsList 中提到的所有客户端 ID 值以匹配子对象（即 UserClients 列表）的用户的场景。

我希望获得准确的 Linq 查询，以便在只有一个用户（用户 1001）符合所需条件的情况下获得预期结果。以下是可以参考的示例代码片段。

using System;
using System.Linq;
using System.Collections.Generic;

namespace ConsoleApp1
{
    class User
    {
        public int UserID { get; set; }
        public List<UserClient> UserClients { get; set; }
    }

    class Client
    {
        public int ClientID { get; set; }
        public int UserID { get; set; }
    }

    class UserClient
    {
        public int ClientID { get; set; }
        public int UserID { get; set; }
        public DateTime StartDate { get; set; }
    }


    class Program
    {
        static void Main(string[] args)
        {            
            List<int> searchClientsList = new List<int> { 1, 2};
            List<User> users = GetTestData();
            var result = users.Where(x => x.UserClients.Any(y => searchClientsList.Contains(y.ClientID) && y.UserID== x.UserID)).ToList(); //To work on Query.
            Console.WriteLine("The above result should return list of users with userclients having all the clientIds mentioned in searchClientsList.");
            Console.WriteLine("In this case, it should return only User1 when searchClientsList is [1,2].");
        }

        private static List<User> GetTestData() {

            User user1 = new User()
            {
                UserID = 1001,
                UserClients = new List<UserClient>() { new UserClient { UserID = 1001, ClientID = 1 }, new UserClient { UserID = 1001, ClientID = 2 } , new UserClient { UserID = 1001, ClientID = 3 } }
            };

            User user2 = new User()
            {
                UserID = 1002,
                UserClients = new List<UserClient>() { new UserClient { UserID = 1002, ClientID = 2 }, new UserClient { UserID = 1002, ClientID = 3 } }
            };
            List <User> users = new List<User>();
            users.Add(user1);
            users.Add(user2);
            return users;

        }
    }
}

Answer 1

我无法弄清楚如何在单个 Linq 查询中执行此操作。

var result = users.ToList();

foreach(int clientId in searchClientsList)
{
    result = result.Where(x => x.UserClients.Any(y => y.ClientID == clientId)).ToList();
}

获取原始列表的副本，然后为 searchClientsList 的每个成员减少它似乎是正确的方法。

Answer 2

就像您在代码中提到的：上述结果应该返回具有 userclients 的用户列表，其中所有的 clientIds 在 searchClientsList 中提到>，所以你应该使用 .All 而不是 .Contains :

List<int> searchClientsList = new List<int> { 1, 2 };
List<User> users = GetTestData();

List<User> result = users
    .Where(x => searchClientsList.All(clientId => x.UserClients.Any(y => y.ClientID == clientId && y.UserID == x.UserID)))
    .ToList();

foreach (var user in result)
{
    Console.WriteLine(user.UserID);
}

希望这对您有帮助。

Linq 根据子对象集合过滤父对象

2 个答案: