LINQ 将列总和添加到列表条目

问题描述

我目前正在开发 .net 5.0 应用程序。

我需要使用 LINQ 来做一个复杂的查询：

• 给定的是 List<Player>
• 我需要转换 List<Player>，但保留所有条目
• 将每支球队的总得分添加到“意甲”中的所有球员

不幸的是，我不知道如何使用 C# LINQ 扩展方法语法正确计算联赛中所有球员的每支球队的总得分。

• 播放器类：

public class Player
{
    public string Name { get; set; }
    public string Team  { get; set; }
    public int score  { get; set; }
    public string League  { get; set; }
    public int TotalTeamscore  { get; set; }
}

• 程序类

public class Program
{
    public static void Main()
    {
        // given is a List<Player> - I need to calculate the Totalscore for each team ONLY for Leage "SerieA"
        var players = new List<Player> {
            new Player { Name = "Alex",Team = "A",score = 10,League = "SerieA",TotalTeamscore = 0 },new Player { Name = "Anna",score = 20,new Player { Name = "Berta",Team = "B",score = 60,new Player { Name = "Benny",score = 40,new Player { Name = "Charlie",Team = "C",League = "PremierLeague",new Player { Name = "Connor",};

        // I need to find a proper way to calculate the TotalTeamscore for each Team in league SerieA and add this score to the players...
        var teamTotalscores = players
                                .Where(p => p.League == "SerieA")
                                .GroupBy(p => p.Team)
                                .Select(p => new Player {
                                    TotalTeamscore = p.Sum(s => s.score)
                                    // score = x.Key ??
                                })
                                .ToList();
        
// desired result: same List<Player> - only the Total Teamscore of a Team in "SerieA" should be calculated for each team and added to each player in a team:
// new Player { Name = "Alex",TotalTeamscore = 30 },// new Player { Name = "Anna",// new Player { Name = "Luke",TotalTeamscore = 100 },// new Player { Name = "Lucy",// new Player { Name = "Charlie",// new Player { Name = "Connor",}

你知道如何解决这个问题吗？

您是否知道如何使用 C# LINQ 扩展方法语法正确计算联赛中所有球员的每支球队的 Totalscore。

解决方法

LINQ 专为查询而设计，而您需要修改集合中的对象。

虽然您可以使用 Enumerable.Select 执行此操作，但标准的 foreach 循环会更合适：

var serieAPlayers = players.Where(p => p.League == "SerieA");

var teamScores = serieAPlayers
    .GroupBy(p => p.Team)
    .ToDictionary(grp => grp.Key,grp => grp.Sum(p => p.Score));

foreach (var player in serieAPlayers) player.TotalTeamScore = teamScores[player.Team];