学习整理！
定义基础类
/// <summary>
/// 球员类
/// </summary>
public class Player
{
public int ID { get; set; }
public string Name { get; set; }
public int Age { get; set; }
/// <summary>
/// 所属位置
/// </summary>
public Location Location { get; set; }
/// <summary>
/// 所属球队
/// </summary>
public Team Team { get; set; }
public int MvpNumber { get; set; }
}
/// <summary>
/// 位置类
/// </summary>
public class Location
{
public string LocationCode { get; set; }
public string LocationName { get; set; }
}
}
/// <summary>
/// 球队类
/// </summary>
public class Team
{
public string TeamCode { get; set; }
public string TeamName { get; set; }
}
添加数据
//初始化测试数据
List<Player> players = new List<Player>()
{
new Player { ID = 1, Name = "Harden", Age = 30,
Location = new Location { LocationCode = "PG", LocationName = "控球" },
Team = new Team { TeamCode = "HOU", TeamName = "休斯顿火箭" }, MvpNumber = 1
},
new Player { ID = 2, Name = "Curry", Age = 29,
Location = new Location { LocationCode = "SG", LocationName = "得分" },
Team = new Team { TeamCode = "GSW", TeamName = "金州勇士" }, MvpNumber = 2
},
new Player { ID = 3, Name = "James", Age = 33,
Location = new Location { LocationCode = "SF", LocationName = "小前" },
Team = new Team { TeamCode = "LAL", TeamName = "洛杉矶湖人" }, MvpNumber = 5
},
new Player { ID = 4, Name = "Zhouqi", Age = 20,
Location = new Location { LocationCode = "PF", LocationName = "大前" },
Team = new Team { TeamCode = "CHN", TeamName = "铁头娃队" }, MvpNumber = 0
},
new Player { ID = 5, Name = "Yao", Age = 36,
Location = new Location { LocationCode = "C", LocationName = "中锋" },
Team = new Team { TeamCode = "CHN", TeamName = "无敌天朝队" }, MvpNumber = 8
}
};
开始测试
引入 using System.Linq;
一、Max/Min(最大值/最小值)
var ageMax = players.Max(u => u.Age);
Console.WriteLine("最大年龄:" + ageMax);
var ageMin = players.Min(u => u.Age);
Console.WriteLine("最小年龄:" + ageMin);
结果：
二、Where条件筛选
Method 1 ：源数据.Where( u => u.属性 筛选条件);
Method 2：from 变量 in 源数据
Where 变量.属性 筛选条件
Select 变量;
ps: 可加ToList()方法带出数据(个人比较Low的解释)
//查询MvpNumber值大于2的球员
//第一种写法
var mvpNum1 = players.Where(u => u.MvpNumber > 2).ToList();
//第二种写法
var mvpNum2 = (from n in players
where n.MvpNumber > 2
select n).ToList();
输出:
三、排序 OrderBy
升序：源数据.OrderBy( u => u.属性).ToList();
降序：源数据.OrderByDescending( u => u.属性).ToList();
ps:必须包含ToList()方法,否则报类型错误
//按年龄升序排序
players = players.OrderBy(u => u.Age).ToList();
//按年龄降序排序
players = players.OrderByDescending(u => u.MvpNumber).ToList();
结果：
四、分组GroupBy
Method 1：源数据.GroupBy( u => u.属性).ToList();
Method 2：from n in 源数据
group n by n.属性
into newGroup
Select newGroup;
//按球队分组
Console.WriteLine("\n方法一：");
var teamGroup = players.GroupBy(u => u.Team.TeamName).ToList();
Console.WriteLine("共有{0}支球队", teamGroup.Count());
foreach (var item in teamGroup)
{
Console.WriteLine("球队名称：{0}", item.Key);
foreach (var n in item)
{
Console.WriteLine(n.ID + "\t" + n.Name + "\t" + n.Age + "\t" +
n.Location.LocationCode + "\t" + n.Location.LocationName + "\t" +
n.Team.TeamCode + "\t" + n.Team.TeamName + "\t" + n.MvpNumber);
}
}
Console.WriteLine("\n方法二：");
var teamGroup2 = (from n in players
group n by n.Team.TeamName
into newGroup
select newGroup).ToList();
Console.WriteLine("共有{0}支球队", teamGroup2.Count());
foreach (var item in teamGroup2)
{
Console.WriteLine("球队名称：{0}", item.Key);
foreach (var n in item)
{
Console.WriteLine(n.ID + "\t" + n.Name + "\t" + n.Age + "\t" +
n.Location.LocationCode + "\t" + n.Location.LocationName + "\t" +
n.Team.TeamCode + "\t" + n.Team.TeamName + "\t" + n.MvpNumber);
}
}
结果：
Linq Group By 用法总结
Key、Count
var q = (from n in players
group n by n.Team.TeamName
into g
select g).ToList();
Console.WriteLine("\n共{0}支球队", q.Count()); //如果上面进行ToList操作，q.Count可以不加();
foreach (var item in q)
{
Console.WriteLine("球队名称：" + item.Key);
}
结果：
Group By中使用Where约束
//30岁以上年龄段分组
var q = (from n in players
group n by n.Age
into g
where g.Key > 30
select g).ToList();
结果：
Group By根据表达式分组
//年龄大于30岁且MVP数量大于1分为一组，否则分在另一组
var q = (from n in players
group n by n.Age > 30 && n.MvpNumber >= 1
into g
select g).ToList();
foreach (var item in q)
{
if (item.Key)
{
Console.WriteLine("满足条件:");
foreach (var n in item)
{
Console.WriteLine(n.ID + "\t" + n.Name + "\t" + n.Age + "\t" +
n.Location.LocationCode + "\t" + n.Location.LocationName + "\t" +
n.Team.TeamCode + "\t" + n.Team.TeamName + "\t" + n.MvpNumber);
}
}
else
{
Console.WriteLine("不满足条件:");
foreach (var n in item)
{
Console.WriteLine(n.ID + "\t" + n.Name + "\t" + n.Age + "\t" +
n.Location.LocationCode + "\t" + n.Location.LocationName + "\t" +
n.Team.TeamCode + "\t" + n.Team.TeamName + "\t" + n.MvpNumber);
}
}
}
结果：
输出：
Group By 多列
var q = (from n in players
group n by new
{
//这里的Key包含Age，Name以及Team信息
n.Age,
n.Name,
n.Team
}
into g
select g).ToList();
结果：