LINQ的高级应用

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本文不想罗列linq的通俗使用方法。因为很多博文都已经写得很详细了。

此处直接贴出源码，如果有需要的朋友可以参考，希望更多的朋友能够补充更多的linq的高级应用。

源码如下：

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading;

 namespace linq
 {
 class Program
 {
 static void Main(string[] args)
 {
 Person[] ps = {
 new Person{Name="jack",Age=,Phone="",PID=},
 new Person{Name="tom",Age=,Phone="235asdg64",PID=},
 new Person{Name="jerry",Age=,Phone="235dasg64",PID=},
 new Person{Name="lily",Age=,Phone="23asdg564",PID=}
 };
 Animal[] ana = {
 new Animal{AID=,Name="dog",PID=},
 new Animal{AID=,Name="cat",PID=},
 new Animal{AID=,Name="dog",PID=},
 new Animal{AID=,Name="chicken",PID=},
 new Animal{AID=,Name="dog",PID=},
 new Animal{AID=,Name="dog",PID=},
 new Animal{AID=,Name="cat",PID=},
 new Animal{AID=,Name="cat",PID=}
 };
 Console.WriteLine("----------------分组排序------------------------");
 //分组
 var result = from p in ps
 group p by p.Age into g//根据p的值对p进行分组，每组放入g变量中
 orderby g.Count() descending
 //g.Key为每一组的“组标识”（比如根据年龄groupby，年龄就是组标识）
 select new { Name = g.Key, Count = g.Count() };
 ps.Where(p => p.Age > );
 foreach (var p in result)
 {
 Console.WriteLine("年龄为："+p.Name + "的人数是：" + p.Count);
 }

 Console.WriteLine("----------------等值连接------------------------");
 //连接 多表查询---下面为等值连接即内连接
 var data = from p in ps
 join a in ana on p.PID equals a.PID
 select new {PID=p.PID,PName=p.Name,PAge=p.Age,PPhone=p.Phone,AID=a.AID,AName=a.Name };
 foreach (var item in data)
 {
 Console.WriteLine(item.PID+"--"+item.PName+"--"+item.PAge+"--"+item.PPhone+"--"+item.AID+"--"+item.AName);
 }
 Console.WriteLine("----------------左连接------------------------");
 //左连接的写法
 var data1 = from p in ps
 join a in ana on p.PID equals a.PID
 into temp //临时表
 from t in temp.DefaultIfEmpty()
 select new { PID = p.PID, PName = p.Name, PAge = p.Age, PPhone = p.Phone, AID =( t!=null?t.AID:), AName = (t!=null?t.Name:"null")};
 foreach (var item in data1)
 {
 Console.WriteLine(item.PID + "--" + item.PName + "--" + item.PAge + "--" + item.PPhone + "--" + item.AID+ "--" + item.AName);
 }

 //lamba本质剖析
 var d1 = from p in ps
 where p.Age>
 select p;
 //Where,Select等均为IEnumerable接口的扩展方法
 var d2 = ps.Where(p => p.Age > ).Select(p => p);
 var d3 = ps.Where(p => p.Age > );
 var d4 = ps.Where((p) => p.Age > );
 //其实where方法内的参数是一个匿名方法或者说是匿名委托 var p=function(parameter){return i>0}
 //系统委托 public delegate TResult Func<in T, out TResult>(T arg);
 //当只有一个参数，方法内只有一行代码时可以简写为 var d3 = ps.Where(p => p.Age > 30);
 var d5 = ps.Where((p) => { return p.Age > ; });

 //lamba在多线程中的应用
 //i => { Console.WriteLine("hhh" +i); }就是一个匿名方法或者说匿名委托
 //Thread t1 = new Thread(i => { Console.WriteLine("hhh" +i); });
 Thread t1 = new Thread((i) => { Console.WriteLine("我是多线程委托实现：" + i); });
 t1.Start();

 //匿名委托的实现方式
 //DelFun dfun=delegate(int i){Console.WriteLine(i);};
 DelFun dfun = (i => { Console.WriteLine("我是匿名委托："+i); });
 dfun();

 Console.Read();
 }
 delegate void DelFun(int i);
 class Person
 {
 public int PID { get; set; }
 public string Name { get; set; }
 public int Age { get; set; }
 public string Phone { get; set; }
 }
 class Animal
 {
 public int AID { get; set; }
 public string Name { get; set; }
 public int PID { get; set; }

 }
 }
 }