LINQ基础

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();
        }
    }
}