List操作之Select

本文是写给C#新手，老手就勿看了，讲的实际上就是LINQ，谢谢一楼的提醒。

很多时候，从一个关系表中挑出一个我们需要的元素列表采用SQL语句是再容易不过的了，其实C#的List中也可以采用类似的方法，虽然List中集成了Select(), Where()等语句，不过如果你的判断规则较为复杂，或者想要看起来一目了然，以下的方法也是可行的：

首先假设你有一个类

public class People
{
    public string Name { get; set; }
    public int Age { get; set; }
}

并且有一些初始化语句

List<People> PeopleList = new List<People>();
PeopleList.Add(new People() { Name = "Haocheng Wu", Age = 24 });
PeopleList.Add(new People() { Name = "Haocheng Wu", Age = 25 });
PeopleList.Add(new People() { Name = "James Wu", Age = 23 });

你就可以采用下面类似于SQL语句的方法进行select

List<string> SubPeopleNameList1 = (from people in PeopleList
                              where people.Name == "Haocheng Wu" && people.Age == 24
                              select people.Name).ToList<string>();

当然你也可以用一行代替

List<string> SubPeopleNameList2 = PeopleList.Where(people => people.Name == "Haocheng Wu" && people.Age == 24).Select(people => people.Name).ToList();

不过显然第一种方法更加一目了然，尤其是当判断条件相当复杂的时候就更加有用了