如何從列表中刪除父母在同一個列表中的項目

Question

我有一個List<Item>。

如何刪除使用LINQ在同一列表中有父母的項目？

如果可能我更喜歡方法鏈表達式。

產品定義：

public class Item { 
     public int Id { get; set; } 
     public int ParentId { get; set; } 
    } 

Answer 1

var Children = List.Where(child => List.Any(parent => parent.Id == child.ParentID)).ToList(); 
List.RemoveAll(child => Children.Contains(child)); 

Answer 2

這可能有助於

List<Item> items = new List<Item>(); 
items.Add(new Item() { Id = 1, ParentId = 2 }); 
items.Add(new Item() { Id = 2, ParentId = 0 }); 
items.Add(new Item() { Id = 3, ParentId = 0 }); 
items.Add(new Item() { Id = 4, ParentId = 1 }); 
items.Add(new Item() { Id = 5, ParentId = 1 }); 
items.Add(new Item() { Id = 6, ParentId = 4 }); 
items.Add(new Item() { Id = 7, ParentId = 4 }); 
items.Add(new Item() { Id = 8, ParentId = 4 }); 
items.Add(new Item() { Id = 9, ParentId = 4 }); 
items.Add(new Item() { Id = 10, ParentId = 4 }); 
items.Add(new Item() { Id = 11, ParentId = 4 }); 

var shouldBeRemove = 
    (from i in items 
    where items.Any(input => input.Id == i.ParentId) 
    select i).ToList(); 

items.RemoveAll(input => shouldBeRemove.Contains(input)); 

//Those who remain 
//item with Id = 2 
//item with Id = 3