标签：http ar 使用 for sp strong div on art
linq中let关键字就是对子查询的一个别名，let子句用于在查询中添加一个新的局部变量，使其在后面的查询中可见。
linq中let关键字实例
1、传统下的子查询与LET关键字的区别
static void Main(string[] args)
{
int[] numbers = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
//传统下的子查询做法
var query = from num in numbers
select num * (from n in numbers
where n % 2 == 0
select n).Count();
//使用LET关键字的做法
var query = from num in numbers
let evenNumbers = from n in numbers
where n % 2 == 0
select n
select num * evenNumbers.Count();
foreach (var item in query)
{
Console.WriteLine(item);
}
Console.Read();
}
2、把每个单词开头包含a或者e的找出来
using System;
using System.Linq;
public class Test
{
static void Main(string[] args)
{
string[] strings = { "A penny saved is a penny earned.", "The aaxly sdj", "the pa is no" };
var query = from sentence in strings
let words = sentence.Split(‘ ‘)//用空格分割成数组
from word in words
let w = word.ToLower()//把每个字母小写
where w[0] == ‘a‘ || w[0] == ‘e‘
select word;
foreach (var s in query)
{
Console.WriteLine(s);
}
Console.ReadLine();
}
}
3、linq实例3
var query = from p in persons
let friendlyName = p.Gender == "男" ? "Mr" : "Ms" + p.Name
select new
{
UserID = p.ID,
FriendName = friendlyName
};
foreach (var item in query)
{
Console.WriteLine("No:{0},Friendly Name:{1}", item.UserID, item.FriendName);
}
4、linq实例4
public class Singer
{
public string Name { set; get; }
public int Age { set; get; }
}
List<Singer> list = new List<Singer>(){
new Singer{Name="zhangs" ,Age=21},
new Singer{Name="zhangs",Age=25},
new Singer{Name="margy",Age=21}
};
var query = from a in list
let b = a.Name
let c=a.Age
where b =="zhangs" & c>21
select a;
foreach (var item in query)
{
Response.Write("姓名: "+item.Name+" 年龄:"+item.Age);
}
//结果 姓名: zhangs 年龄:25
//使用let 建立了个范围变量，这个范围变量在后续的where子句中使用，如果不使用let子句，where子句的表达式将写成这样：
//where a.Name=="zhangs" & a.Age>21</span>
标签：http ar 使用 for sp strong div on art
原文地址：http://www.cnblogs.com/ranran/p/4059324.html
