c# - 如果满足父列表中子项列表中的列表内的属性，则返回父列表中的项

Question

我正在尝试用下面给出的代码中的 LINQ 替换 foreach。我已经更正了代码并添加了一些演示数据。希望这能澄清一点。

我必须以这样一种方式进行过滤，即 LINQ 查询返回包含至少一个满足爱好条件检查的项目的父项目。

var parents = new List<Parent>
{
    new Parent
    {
        ParentName = "Tom",
        Children = new List<Child>
        {
            new Child
            {
                ChildName = "Ram",
                Hobbies = new List<Hobby>
                {
                    new Hobby
                    {
                        Name = "Reading",
                        Code = "1"
                    },
                    new Hobby
                    {
                        Name = "Hiking",
                        Code = "2"
                    }
                 }
            }
        }
    },
    new Parent
    {
        ParentName = "Harry",
        Children = new List<Child>
        {
            new Child
            {
                ChildName = "Som",
                Hobbies = new List<Hobby>
                {
                    new Hobby
                    {
                        Name = "Exercise",
                        Code = "2"
                    },
                    new Hobby
                    {
                        Name = "Hiking",
                        Code = "3"
                    }
                }
            }
        }
    }
};
var parentsWithKidsWhoDontExercise = new List<Parent>();
foreach(var parent in parents)
{
    foreach(var child in parent.Children)
    {
        var favoriteHobby = child.Hobbies.FirstOrDefault();
        if(favoriteHobby.Name !="Exercise")
        {
            parentsWithKidsWhoDontExercise.Add(parent);
        }
    }
}

标签： c#linq

Answer 1

我今天早些时候回答了一个类似的问题。请参阅下面的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;


namespace ConsoleApplication1
{
    class Program
    {
       static void Main(string[] args)
        {

           List<Parent> parents = new List<Parent>() {
               new Parent() { ID = 123, Children = new List<Child>() {
                       new Child() { ID = 2000, Hobbies = new List<Hobby>() {
                           new Hobby()  { HobbyName = "Stamp Collection", ID = 3000},
                           new Hobby()  { HobbyName = "Coins Collection", ID = 3001},
                           new Hobby()  { HobbyName = "Butterfly Collection", ID = 3002}
                           }
                       },
                       new Child() { ID = 2001, Hobbies = new List<Hobby>() {
                           new Hobby()  { HobbyName = "Stamp Collection", ID = 3000},
                           }
                       },
                       new Child() { ID = 2002, Hobbies = new List<Hobby>() {
                           new Hobby()  { HobbyName = "Coins Collection", ID = 3001},
                           }
                       },
                       new Child() { ID = 2003, Hobbies = new List<Hobby>() {
                           new Hobby()  { HobbyName = "Butterfly Collection", ID = 3002}
                           }
                       }
                   }
               }
           };

           var parentItems = parents.SelectMany(x => x.Children.SelectMany(y => y.Hobbies.Select(z => new { parentId = x.ID, childId = y.ID, hobbyName = z.HobbyName, hobbyId = z.ID }))).ToList();
        }
    }
    public class Parent
    {
        public int ID { get;set;}
        public List<Child> Children  { get;set;}
    }
    //Nested class 1
    public class Child
    {
        public int ID  { get; set; }
        public List<Hobby> Hobbies { get; set; }
    }
    //Nested class 2
    public class Hobby
    {
        public int ID  { get; set; }
        public string HobbyName  { get; set; }
    }


}