使用LINQ获得一个名单，其中项目;＆gt;中不在另一个列表＆LT;＆GT; [英] Use LINQ to get items in one List<>, that are not in another List<>

问题描述

我会假设有一个简单的LINQ查询要做到这一点，我只是不完全知道如何。请参见下面的code段，注释解释了什么是我想要做的：

 类节目
{
    静态无效的主要（字串[] args）
    {
        名单＆LT;人＆GT; peopleList1 =新的名单，其中，人物＆GT;（）;
        peopleList1.Add（新的Person（）{n = 1}）;
        peopleList1.Add（新的Person（）{n = 2}）;
        peopleList1.Add（新的Person（）{n = 3}）;

        名单＆LT;人＆GT; peopleList2 =新的名单，其中，人物＆GT;（）;
        peopleList2.Add（新的Person（）{n = 1}）;
        peopleList2.Add（新的Person（）{n = 2}）;
        peopleList2.Add（新的Person（）{n = 3}）;
        peopleList2.Add（新的Person（）{n = 4}）;
        peopleList2.Add（新的Person（）{n = 5}）;

        //我想执行LINQ查询给我的一切
        //市民对peopleList2'不在'peopleList1
        //这个例子应该给我两个人（ID = 4和ID = 5）
    }
}

类Person
{
    公众诠释ID {获得;组; }
}
 

解决方案

  VAR的结果= peopleList2.Where（P =＆GT;！peopleList1.Any（P2 =＆GT; p2.ID = = p.ID））;
 

I would assume there's a simple LINQ query to do this, I'm just not exactly sure how. Please see code snippet below, the comment explains what I'd like to do:

class Program
{
    static void Main(string[] args)
    {
        List<Person> peopleList1 = new List<Person>();
        peopleList1.Add(new Person() { ID = 1 });
        peopleList1.Add(new Person() { ID = 2 });
        peopleList1.Add(new Person() { ID = 3 });

        List<Person> peopleList2 = new List<Person>();
        peopleList2.Add(new Person() { ID = 1 });
        peopleList2.Add(new Person() { ID = 2 });
        peopleList2.Add(new Person() { ID = 3 });
        peopleList2.Add(new Person() { ID = 4 });
        peopleList2.Add(new Person() { ID = 5 });

        //I would like to perform a LINQ query to give me all
        //of the people in 'peopleList2' that are not in 'peopleList1'
        //this example should give me two people (ID = 4 & ID = 5)
    }
}

class Person
{
    public int ID { get; set; }
}

解决方案

var result = peopleList2.Where(p => !peopleList1.Any(p2 => p2.ID == p.ID));

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