c# - 加入两个列表比较它们的元素属性

Question

public class Person()
    {
    int ID;
    string Name;
    DateTime ChangeDate
    } 



var list1 = new List<Person>
    {
        new Person { ID= 1, Name = "Peter", ChangeDate= "2011-10-21" },
        new Person { ID= 2, Name = "John",  ChangeDate= "2011-10-22" },
        new Person { ID= 3, Name = "Mike",  ChangeDate= "2011-10-23" },
        new Person { ID= 4, Name = "Dave",  ChangeDate= "2011-10-24" }
    };

 var list2 = new List<Person>
    {
        new Person { ID= 1, Name = "Pete",  ChangeDate= "2011-10-21" },
        new Person { ID= 2, Name = "Johny", ChangeDate= "2011-10-20" },
        new Person { ID= 3, Name = "Mikey", ChangeDate= "2011-10-24" },
        new Person { ID= 5, Name = "Larry", ChangeDate= "2011-10-27" }
    };

作为输出，我希望有 list1 + list2 =

    Person { ID= 1, Name = "Peter", ChangeDate= "2011-10-21" },
    Person { ID= 2, Name = "John",  ChangeDate= "2011-10-22" },
    Person { ID= 3, Name = "Mikey", ChangeDate= "2011-10-24" },
    Person { ID= 4, Name = "Dave",  ChangeDate= "2011-10-24" }
    Person { ID= 5, Name = "Larry", ChangeDate= "2011-10-27" }

算法是这样的。加入两个列表。如果列表的元素具有相同的 ID，则按 ChangeDate 比较它们并取日期较大的一个。如果 ChangeDate 相等，则取其中任何一个，但不能同时取两者。也许连接两个列表比使用 lambda 过滤它们更容易。我试过了，但总是出现一些丑陋的代码:/

有人知道吗？

Answer 1

林奇

var q = from person in list1.Concat(list2)
        group person by person.ID into g
        select g.OrderByDescending(p => p.ChangeDate).First();