的GroupBy复杂的查询

Question

我已经创建了统计页面视图模型如下：

public class StatsSeasonViewModel 
{ 
    public int player_id { get; set; } 
    public string player_name { get; set; } 
    public int games_played { get; set; } 
    public int total_first { get; set; } 
    public int total_second { get; set; } 
    public int total_third { get; set; } 
    public int total_wickets { get; set; } 
    public double avg_wickets { get; set; } 
    public int total_points { get; set; } 
    public double avg_points { get; set; } 
} 

我有一个复杂的LINQ语句来填充模型。我觉得这可能是简单的，但我不知道如何做到这一点：

const int first_place = 5; 
const int second_place = 3; 
const int third_place = 1; 

var model = 
from s in _db.Stats 
join p in _db.Players 
on s.player_id equals p.player_id 
where s.season_id == current_season 
select new StatsSeasonViewModel 
{ 
    player_id = p.player_id, 
    player_name = p.name, 
    games_played = (from st1 in _db.Stats 
        where st1.player_id == s.player_id 
        select st1).Count(), 
    total_first = (from st2 in _db.Stats 
        where st2.player_id == s.player_id && st2.place == 1 
        select st2).Count(), 
    total_second = (from st3 in _db.Stats 
        where st3.player_id == s.player_id && st3.place == 2 
        select st3).Count(), 
    total_third = (from st4 in _db.Stats 
        where st4.player_id == s.player_id && st4.place == 3 
        select st4).Count(), 
    total_wickets = (from st5 in _db.Stats 
         where st5.player_id == s.player_id 
         select st5.wickets).Sum(), 
    avg_wickets = (from st5 in _db.Stats 
        where st5.player_id == s.player_id 
        select st5.wickets).Sum()/
        (from st1 in _db.Stats 
        where st1.player_id == s.player_id 
        select st1).Count(), 
    total_points = (from st5 in _db.Stats 
        where st5.player_id == s.player_id 
        select st5.wickets).Sum() + 
        (
         (from st2 in _db.Stats 
          where st2.player_id == s.player_id && st2.place == 1 
          select st2).Count() 
        ) * first_place + 
        (
         (from st3 in _db.Stats 
          where st3.player_id == s.player_id && st3.place == 2 
          select st3).Count() 
        ) * second_place + 
        (
         (from st4 in _db.Stats 
          where st4.player_id == s.player_id && st4.place == 3 
          select st4).Count() 
        ) * third_place, 
    avg_points = (
        (from st5 in _db.Stats 
         where st5.player_id == s.player_id 
         select st5.wickets).Sum() + 
        (
         (from st2 in _db.Stats 
          where st2.player_id == s.player_id && st2.place == 1 
          select st2).Count() 
        ) * first_place + 
        (
         (from st3 in _db.Stats 
          where st3.player_id == s.player_id && st3.place == 2 
          select st3).Count() 
        ) * second_place + 
        (
         (from st4 in _db.Stats 
          where st4.player_id == s.player_id && st4.place == 3 
          select st4).Count() 
        ) * third_place 
       )/
       (from st1 in _db.Stats 
        where st1.player_id == s.player_id 
        select st1).Count() 
}; 

所以我现在最大的问题是，我需要通过这个查询做一组，使其不会显示重复。但是，当我尝试添加组时，然后我迷失了如何在SELECT之后执行其余查询。我如何通过上面的查询来完成一个组，并获得我需要的结果？

编辑：FWIW这里是结果我得到：http://ecl.moyl.com/Home/Stats

第二个问题是当然的查询本身的复杂性。有没有更简单的方法来做到这一点？

Answer 1

有一对夫妇的方式把事情简单化，但回答您的主要问题：

var search = from st2 in _db.Stats 
    where st2.player_id = s.player_id 
    group st2 by st2.player_id 

你会遍历每个小组获得IGrouping<TKey, TElement>得到个别情况（ref）。

for (var playerGroup in search) 
{ 
    Console.WriteFormat("{0}: {1}\n", playerGroup.Key, playerGroup.Count()); 
} 

如果您使用稍微不同的方式编写计数/总和，那么您的代码可能会更具可读性。

例如，这个：

games_played = (from st1 in _db.Stats 
       where st1.player_id == s.player_id 
       select st1).Count(), 
total_wickets = (from st5 in _db.Stats 
        where st5.player_id == s.player_id 
        select st5.wickets).Sum() 

可能成为这样的：

var filter = st => st.player_id == s.player_id; // reuse this over and over 

games_played = _db.Stats.Where(filter).Count(), 
total_wickets = _db.Stats.Where(filter).Sum(st5 => st5.wickets) 

---

事实上， “有你的蛋糕和熊掌兼得”，整个过滤器变得不必要，当你使用group by语句。你必须改变你创建你的模型的方式，这样你就可以将IGrouping<int,Stat>（假设这就是类型）传递给构造函数。在这种方法的总体查询看起来是这样的：

const int first_place = 5; 
const int second_place = 3; 
const int third_place = 1; 

var model = 
    from s in _db.Stats 
    join p in _db.Players 
    on s.player_id equals p.player_id 
    where s.season_id == current_season 
    group st by st.player_id into group 
    select new StatsSeasonViewModel(group) 

现在你StatsSeasonViewModel负责基于组

public StatsSeasonViewModel(IGrouping<int,Stat> playerStats) 
{ 
    player_id = playerStats.Key; 
    games_played = playerStats.Count(); 
    total_wickets = playerStats.Sum(st=>st.wickets); 
    // .... 
} 

Answer 2

您正在使用过时的方式在MVC中编写Linq。使用的DbContext通过创建一个需要玩家ID作为变量的方法很容易地找到播放器和使用distinct返回不同的值，避免重复：

var player = _db.Players.Where(p => p.player_id == Id); 

然后由处理属性的λ-加入与玩家统计数据表格：

var st1 in _db.Stats.Where(st1 => st1.player_id == player.player_id).Distinct().Count(); 

编辑：

我改变了一点，因为你想在第二个表达不同，因为第一已经会发现一个独特的价值