C#Linq的使用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;
using System.Collections;


namespace LinqDemos
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] num = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 1000 };
            var n = from number in num where number % 2 == 0 select number;
            foreach (int a in n)
            {
                Console.WriteLine(a.ToString());
            }
            ArrayList arr = new ArrayList();
            arr.Add(new Student { Name = "张三", Age = 12, Addresss = "莆田" });
            arr.Add(new Student { Name = "王三", Age = 12, Addresss = "福州" });
            var data = from Student stu in arr where stu.Name == "王三" select stu;
            foreach (Student item in data)
            {
                Console.WriteLine(item.Name);
            }
        }
    }
    public class Student
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public string Addresss { get; set; }

    }

}

Linq是一种面向对象的查询方式，它和SQL语句及其类似，sql写法 select * from 表  Linq写法 from n in 数据源 select n;

为什么不跟sql写法一样将select一同写在语句的开头呢？主要是当时做IDE时考虑到智能感应,将select写在语句头不利于编程环境的智能感应，其中的奥妙自行百度理解哈，这边不详讲

Linq的查询对象可以是所有实现了IEnumerable的类型，比如数组，数据库集合(DataTable,DataSet...)，Arraylist,List,

用Linq这种写法对于我们来说更加的直观，当然你也可以使用foreach和for。相对于这两种查询语句,Linq执行的效率和性能要优胜,

Linq>foreach>for