创建一个控制台程序，用于打印结果：
using System; using System.Collections.Generic; using System.Linq; namespace LinqStudyDemo { class Program { static void Main(string[] args) { //初始化武林高手 var masters = new List<MartialArtsMaster>(){ new MartialArtsMaster() { Id=1,Name="黄蓉",Age=18,Menpai="丐帮",Kongfu="打狗棒法",Level=9 }, new MartialArtsMaster() { Id=2,Name="洪七公",Age=70,Menpai="丐帮",Kongfu="打狗棒法",Level=10 }, new MartialArtsMaster() { Id=3,Name="郭靖",Age=22,Menpai="丐帮",Kongfu="降龙十八掌",Level=10 }, new MartialArtsMaster() { Id=4,Name="任我行",Age=50,Menpai="明教",Kongfu="吸星大法",Level=1 }, new MartialArtsMaster() { Id=5,Name="东方不败",Age=35,Menpai="明教",Kongfu="葵花宝典",Level=10 }, new MartialArtsMaster() { Id=6,Name="林平之",Age=23,Menpai="华山",Kongfu="葵花宝典",Level=7 }, new MartialArtsMaster() { Id=7,Name="岳不群",Age=50,Menpai="华山",Kongfu="葵花宝典",Level=8 } }; //初始化武学 var kongfus = new List<Kongfu>() { new Kongfu(){KongfuId=1,KongfuName="打狗棒法",Lethality=90 }, new Kongfu(){KongfuId=2,KongfuName="降龙十八掌",Lethality=95 }, new Kongfu(){KongfuId=3,KongfuName="吸星大法",Lethality=99 }, new Kongfu(){KongfuId=4,KongfuName="葵花宝典",Lethality=100 } }; //方法一(使用linq中的查询表达式) var GaiBangMasters = from m in masters where m.Level > 9 && m.Menpai == "丐帮" select m; foreach (var item in GaiBangMasters) { var GaiBangResult = item.Id + " " + item.Name + " " + item.Menpai + " " + item.Kongfu + " " + item.Level; Console.WriteLine(GaiBangResult); } Console.WriteLine("---------------------------------------"); //方法二(使用linq中的lambda表达式) var GaiBangMasters2 = masters.Where(m => m.Level > 9 && m.Menpai == "丐帮"); foreach (var item in GaiBangMasters2) { var GaiBangResult = item.Id + " " + item.Name + " " + item.Menpai + " " + item.Kongfu + " " + item.Level; Console.WriteLine(GaiBangResult); } } } /// <summary> /// 武林高手 /// </summary> class MartialArtsMaster { public int Id { get; set; } public string Name { get; set; } public int Age { get; set; } public string Menpai { get; set; } public string Kongfu { get; set; } public int Level { get; set; } } /// <summary> /// 武学 /// </summary> class Kongfu { public int KongfuId { get; set; } public string KongfuName { get; set; } public int Lethality { get; set; } } }执行结果：
方法一和方法二的执行结果是一样的，都是查询出丐帮中武功级别在9级以上的武林高手信息。
实例二：根据条件筛选信息
Console.WriteLine("杀伤力大于90的武林高手信息:"); var GaiBangMasters3 = from m in masters from k in kongfus where m.Kongfu == k.KongfuName && k.Lethality > 90 orderby m.Level select m.Id + " " + m.Name + " " + m.Menpai + " " + m.Kongfu + " " + m.Level + " " + k.Lethality; foreach (var item in GaiBangMasters3) { Console.WriteLine(item); }执行结果：
实例三：统计武林排行榜
Console.WriteLine("武林排行榜:"); var GaiBangMasters4 = from m in masters from k in kongfus where m.Kongfu == k.KongfuName orderby m.Level * k.Lethality descending, m.Name select m.Id + " " + m.Name + " " + m.Menpai + " " + m.Kongfu + " " + m.Level * k.Lethality; foreach (var item in GaiBangMasters4) { Console.WriteLine(item); }查询语句也可以用join来进行关联：
var GaiBangMasters4 = from m in masters join k in kongfus on m.Kongfu equals k.KongfuName orderby m.Level * k.Lethality descending, m.Name select m.Id + " " + m.Name + " " + m.Menpai + " " + m.Kongfu + " " + m.Level * k.Lethality;执行结果：
实例四：查询出武林英雄中能力最强的人
Console.WriteLine("武林最强王者:"); var GaiBangMasters4 = (from m in masters join k in kongfus on m.Kongfu equals k.KongfuName orderby m.Level * k.Lethality descending, m.Name select m.Id + " " + m.Name + " " + m.Menpai + " " + m.Kongfu + " " + m.Level * k.Lethality).FirstOrDefault(); Console.WriteLine(GaiBangMasters4);执行结果：
实例五：统计各门派的人数
Console.WriteLine("统计各门派的人数:"); var GaiBangMasters5 = from m in masters group m by m.Menpai into g orderby g.Key select new { menpai = g.Key, count = g.Count() }; foreach (var item in GaiBangMasters5) { Console.WriteLine("门派:" + item.menpai + ", 人数:" + item.count); }执行结果：
实例六：linq中量词的使用(any，all，contains)
var kxbd = from m in masters where m.Kongfu == "葵花宝典" select new { m.Name, m.Menpai, m.Kongfu }; Console.WriteLine("练习葵花宝典的大侠:"); foreach (var item in kxbd) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); } Console.WriteLine(); var isHaveMJ = kxbd.Any(m => m.Menpai == "明教"); Console.WriteLine("练习葵花宝典的是否有明教中人? " + (isHaveMJ ? "有" : "没有")); Console.WriteLine(); var isAllMJ = kxbd.All(m => m.Menpai == "明教"); Console.WriteLine("练习葵花宝典的都是明教中人? " + (isAllMJ ? "是" : "不是")); Console.WriteLine(); var ouYangFeng = new MartialArtsMaster() { Id = 8, Name = "欧阳锋", Age = 40, Menpai = "白驼山庄", Kongfu = "蛤蟆功", Level = 10 }; var huangRong = masters[0]; var isOuYangFeng = masters.Contains(ouYangFeng); var isHuangRonng = masters.Contains(huangRong); Console.WriteLine("欧阳锋是否是大侠? " + (isOuYangFeng ? "是" : "不是")); Console.WriteLine("黄蓉是否是大侠? " + (isHuangRonng ? "是" : "不是"));执行结果：
实例七：完成分页操作
int pageSize = 3;//每页显示记录数 int totalPage = (int)Math.Ceiling(masters.Count() / (double)pageSize);//总页数 for (int i = 0; i < totalPage; i++) { var pageMarster = ( from m in masters join k in kongfus on m.Kongfu equals k.KongfuName orderby m.Level * k.Lethality descending, m.Name select new { m.Name, m.Menpai, m.Kongfu, kill = m.Level * k.Lethality }).Skip(pageSize * i).Take(pageSize); Console.WriteLine("第" + (i + 1) + "页"); Console.WriteLine("姓名 门派 武功 杀伤力"); foreach (var item in pageMarster) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu + " " + item.kill); } Console.WriteLine(); }执行结果：
实例八：linq中集合操作符的使用（Intersect，Union，Concat，Except）
Console.WriteLine("集合一:明教派的大侠"); var result1 = from m1 in masters where m1.Menpai == "明教" select m1; foreach (var item in result1) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); } Console.WriteLine(); Console.WriteLine("集合二:练习葵花宝典的大侠"); var result2 = from m2 in masters where m2.Kongfu == "葵花宝典" select m2; foreach (var item in result2) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); } Console.WriteLine(); Console.WriteLine("集合操作符:Intersect,求两个集合的交集"); var selectMaster1 = ( from m1 in masters where m1.Menpai == "明教" select m1 ).Intersect( from m2 in masters where m2.Kongfu == "葵花宝典" select m2 ); foreach (var item in selectMaster1) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); } Console.WriteLine(); Console.WriteLine("集合操作符:Union,求两个集合的并集,去重"); var selectMaster2 = ( from m1 in masters where m1.Menpai == "明教" select m1 ).Union( from m2 in masters where m2.Kongfu == "葵花宝典" select m2 ); foreach (var item in selectMaster2) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); } Console.WriteLine(); Console.WriteLine("集合操作符:Concat,求两个集合的并集,没有去重"); var selectMaster3 = ( from m1 in masters where m1.Menpai == "明教" select m1 ).Concat( from m2 in masters where m2.Kongfu == "葵花宝典" select m2 ); foreach (var item in selectMaster3) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); } Console.WriteLine(); Console.WriteLine("集合操作符:Except,求两个集合的差集"); var selectMaster4 = ( from m2 in masters where m2.Kongfu == "葵花宝典" select m2 ).Except( from m1 in masters where m1.Menpai == "明教" select m1); foreach (var item in selectMaster4) { Console.WriteLine(item.Name + " " + item.Menpai + " " + item.Kongfu); }执行结果：
实例九：Linq查询操作之聚合操作(count,max,min,sum,average,aggregate,longcount)
int[] numbers = { 1, 2, 3, 4, 5, 6, 7 }; int x1 = numbers.Aggregate((n1, n2) => n1 + n2);//28 //int x2 = numbers.Aggregate((n1, n2) => n1 * n2);//5040 int y1 = numbers.Count();//7 //int y2 = numbers.Count(c => c > 3);//4 long z = numbers.LongCount();//7 int sum = numbers.Sum();//28 int max = numbers.Max();//7 int min = numbers.Min();//1 double avg = numbers.Average();//4 Console.WriteLine("Linq聚合操作之Aggregate,用途:对集合元素进行自定义的聚合计算,结果为:" + x1); Console.WriteLine("Linq聚合操作之Count,用途:求集合元素的个数(32位),结果为:" + y1); Console.WriteLine("Linq聚合操作之LongCount,用途:求集合元素的个数(64位),结果为:" + z); Console.WriteLine("Linq聚合操作之Sum,用途:求集合元素的合计值,结果为:" + sum); Console.WriteLine("Linq聚合操作之Max,用途:求集合元素的最大值,结果为:" + max); Console.WriteLine("Linq聚合操作之Min,用途:求集合元素的最小值,结果为:" + min); Console.WriteLine("Linq聚合操作之Average,用途:求集合元素的平均数,结果为:" + avg);执行结果：
关于聚合操作函数的详细用法参考：https://www.cnblogs.com/yplong/p/5421830.html
