linq中let关键字学习

linq中let关键字学习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

C# 代码 复制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

C# 代码 复制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

C# 代码 复制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

C# 代码 复制public class Singer { public string Name { set; get; }