using System;
using System.Collections.Generic;
using
System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Lambda表达式
{
class Program
{
static void
Main(string[] args)
{
}
static List<Person> GetPersonList()
{
return new List<Person>() {
new Person
(){ Age =1,Name ="小白01",ID=1,Gender =true},
new Person (){Age
=2,Name ="小白02",ID=2,Gender =false},
new Person (){Age =3,Name
="小白03",ID=3,Gender =true}
};
}
static List<PersonToy> GetPersonToyList()
{
return new List<PersonToy>() {
new PersonToy(){
PersonToyID=1,Name="小明"},
new PersonToy (){PersonToyID =2,Name ="小白"},
new
PersonToy (){PersonToyID =3,Name ="小红"},
new PersonToy (){PersonToyID =4,Name
="小黑"}
};
}
#region Lambda表达式
/// <summary>
///
Lambda表达式和Lambda语句
/// </summary>
static void
TestLambda()
{
List<Person> list =
GetPersonList();
list.ForEach(d =>
Console.WriteLine(d.Name));
//Lambda表达式
list.FindAll(d =>
d.Age > 1);
list.Sort((x, y) => x.Age - y.Age);
var it = list.Select(p => new smallperson { Name = p.Name });
//语句Lambda语句
var it1 = list.Select(p =>
{
//如果存在多个语句就不能省略{}大括号 也不能省略return
smallperson sp = new
smallperson();
sp.Name = p.Name;
return
sp;
});
}
#endregion
/// <summary>
/// 标准查询方法 ----Where查询
///
</summary>
static void SQOWhere()
{
List<Person> list = GetPersonList();
//在集合中筛选出符合条件的数据
List<Person> list2 = list.Where(p => p.Gender ==
false && p.Age > 1 && p.Age < 3).ToList();
list.ForEach(p => Console.WriteLine(p.Name));
}
/// <summary>
/// 标准查询运算符 select
投射方法（返回一个新的集合）
/// </summary>
static void SQOSelect()
{
List<Person> list = GetPersonList();
List<smallperson> list2 = list.Where(p => p.Gender == false).Select(p
=> new smallperson() { Name = p.Name }).ToList();
}
/// <summary>
/// 标准查询运算符 Order 排序方法
返回一个新的集合
/// </summary>
static void SQOOrder()
{
List<Person> list = GetPersonList();
List<Person >listSorted= list.OrderBy(p =>
p.Age).ThenByDescending(p=>p.ID ).ToList ();//按照年龄进行排序（升序）
// list
.OrderByDescending 倒序
list.ForEach(p=>Console .WriteLine(p.Age.ToString ()));
}
/// <summary>
/// 标准运算符--连接集合
///
</summary>
static void TestJoin()
{
List<Person> listperson = GetPersonList();
List<PersonToy> listPersontToy = GetPersonToyList();
var
listJoin= listperson .Join
(listPersontToy,d=>d.ID,t=>t.PersonToyID,(d,t)=>new {ID=d.ID
,ToyName=t.Name,Name=d.Name}).ToList ();
listJoin.ForEach(a=>Console .WriteLine (a.ID.ToString
()+","+a.ToyName));
}
/// <summary>
/// 标准查询运算符 GroupBy为集合分组
///
/// </summary>
static void SQOGroupBy()
{
List<Person> list = GetPersonList();
//按照性别进行分组
IEnumerable <IGrouping <bool ,Person >>it=
list.GroupBy(p => p.Gender);
//根据姓名进行分组
IEnumerable<IGrouping<string, Person>>
it2 = list.GroupBy(p=>p.Name );
// var it2=
list.GroupBy(p=>p.Name );
IList<IGrouping<bool, Person>> listGroup =
it.ToList();
foreach (var group in listGroup)
{
Console.WriteLine(group .Key.ToString ());
foreach (var item in group)
{
Console.WriteLine(item .Name +","+item .Age);
}
Console.WriteLine("------------------------------------");
}
}
/// <summary>
/// 标准运算符=Skip -Take分页数据
///
</summary>
static void SQOPagedList()
{
List<Person> list = GetPersonList();
}
/// <summary>
///Linq语句 ，编译后会生成对应的标准查询 运算符
linq是一种类似sql的一种更加友好的语法糖 语法而已
/// </summary>
static void
TestLinq()
{
List<Person> list =
GetPersonList();
List<PersonToy>listtoy=GetPersonToyList();
var query = from
li in list select li;//从老集合中每一个元素 存入一个新的集合
//where
var query1
= from li in list where li.Gender == true select li;
//order
descending倒序 aescending正序
var query2 = from li in list orderby li.Gender
orderby li.Age descending select li;
//join链接查询
var
query3=from li in list join t in listtoy on li .ID equals t.PersonToyID select
new {Name=li .Name };
//分组查询
var query4 = from li in list
group li by li.Gender;
}
}
public class smallperson
{
public string Name
{ get; set; }
}
}
原文地址：http://www.cnblogs.com/sumg/p/3743544.html
