LINQ基础

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Linq是微软提供给我们的扩展方法,以下是常用的方法

var i=6 ; var b="aaa"; var p=new {Age=44,Name="胡大"};//var 会自动帮你推导是那种类型的

1.LINQ

var  e2=arr.where(i=>i>0).Orderby(i=>i).Select(i=>"["+i+"]");foreach(var i in e2){  Console.WriteLine(i);}

2.LINQ的最常用的写法

var e3=from i in arr            where i>0            orderby i            select "["+i+"]";foreach(var i in e3){   Console.WriteLine(i);}

using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace LINQ练习{    class Program    {        static void Main(string[] args)        {            //将字符串数组中长度小于5的元素返回            //string[] arr = { "fdsafd","lyan","jiaolili","liyancheng","liyanhong"};            //var e3 = from i in arr            //         where i.Length < 5            //         select i;            //foreach (var i in e3)            //{            //    Console.WriteLine(i);            //}            Console.WriteLine("=================================");            //将一个字符串中都是大于100的返回            //string[] strs = {"323","22","45","123" };            //var e1 = from i in strs            //         let n=Convert.ToInt32(i)            //         where n > 100            //         select n;            //foreach (var i in e1)            //{            //    Console.WriteLine(i);            //}            //将一个姓名为Key,年龄为value的Dictionary的年龄大于20的            //人的姓名用,分割打印出来            //Dictionary<string, int> dict = new Dictionary<string, int>();            //dict["李艳"] = 33;            //dict["焦时"] = 23;            //dict["小艳"] = 12;            //dict["小丽"] = 5;            //var e2 = from key in dict.Keys            //         where dict[key] > 20            //         select key;            //Console.WriteLine(string.Join(",", e2.ToArray()));            //将ajax,javascript,jquery每个单词加上【】输出出来            var s = "ajax,javascript,jquery";            string[] strs = s.Split(',');            var e4 = from i in strs                     select "【" + i + "】";            foreach (var i in e4)            {                Console.WriteLine(i);            }            Console.ReadKey();        }    }}