基于键 C# 合并两个列表

Question

我有班级奖励，我可以保留每场比赛的用户资金。 我有两个列表，我需要以某种方式连接起来。我在下面写了示例列表和期望的结果。

public class Reward
{
    public int Game { get; set; }
    public int User { get; set; }
    public int Money { get; set; }

    public Reward Merge(Reward p)
    {
       return new Reward { Game = this.Game, User = this.User, Money = this.Money + p.Money};
    }
}

    IList<Reward> list1 = new List<Reward>();
    list1.Add(new Reward {Game = 1, User = 1, Money = 10});
    list1.Add(new Reward { Game = 1, User = 2, Money = 20 });
    list1.Add(new Reward { Game = 1, User = 3, Money = 30 });


    IList<Reward> list2 = new List<Reward>();
    list2.Add(new Reward { Game = 2, User = 1, Money = 15 });
    list2.Add(new Reward { Game = 2, User = 2, Money = 25 });
    list2.Add(new Reward { Game = 2, User = 4, Money = 35 });

结果列表应该是

User Money
1    25
2    45
3    30
4    35

我尝试的

IList<Reward> listConcat = list1.Concat(list2)
                .GroupBy(u=> u.User)
                .Select(???)
                .ToList();

但如何？

Answer 1

您使用 GroupBy 的方式是正确的，这应该可以完成工作：

IEnumerable<Reward> result =
    from r in list1.Concat(list2)
    group r by r.User into groupedRewards
    select new Reward
    {
        Game = 0,   //what game to use?
        User = groupedRewards.Key,
        Money = groupedRewards.Sum(r => r.Money)
    };

编辑：与 lambda 表达式相同：

IEnumerable<Reward> result = list1.Concat(list2)
    .GroupBy(u => u.User)
    .Select(g => new Reward
    {
        Game = 0,  //what game to use?
        User = g.Key,
        Money = g.Sum(r => r.Money)
    });

Answer 2

这不是很漂亮，但是很有效。

var listConcat = list1.Concat(list2)
                .GroupBy(u=> u.User)
                .Select(rewards => new Reward { 
                                                User = rewards.Key, 
                                                Money = rewards.Select(reward => reward.Money).Sum() 
                                              }
                       )
                .ToList();

Answer 3

使用.GroupBy，您将获得IGrouping列表，因此选择如下所示：

IEnumerable<Reward> listConcat = list1.Concat(list2)
                                .GroupBy(x => x.User)
                                .Select(x => new Reward { User= x.Key, Money=x.Sum(y => y.Money) });

Answer 4

我想象一个接近您正在寻找的答案看起来像这样：

var catList = list1.Concat(list2)
                   .GroupBy (x => x.User)
                   .Select (y => new Reward{Game = 0, Money = y.Sum (z => z.Money), 
                                User =  y.Key})
                   .ToList();

至于要使用哪个游戏，您可能会考虑匿名选择（即

.Select(new {Money = y.Sum (z => z.Money), User =  y.Key})

这将为您提供一个匿名类型，其中包含您希望使用的信息。如果您是要将其传递出该方法，但是，最佳实践是为其指定类型，或者仅了解游戏 0 是所有游戏的超集。

Answer 5

IList<Reward> listConcat = list1.Concat(list2)
                .GroupBy(person => person.User)
                .Select(group => group.Aggregate((rewardone, rewardtwo) => rewardone.Merge(rewardtwo)))
                .ToList();

Answer 6

请将行更改

 return new Reward { Game = this.Game, User = this.User, Money = this.Money + p.User

为：

 return new Reward { Game = this.Game, User = this.User, Money = this.Money + p.Money