从 linq 查询返回多个计数

Question

我有两个字符串数组，其中包含请求中的冠军名称。我想计算其中一支球队包含 request.TeamChampionNames 中的冠军而另一支球队包含 request.EnemyChampionNames 中的冠军的比赛的胜负。一场比赛只有 2 支球队。每个冠军都是独一无二的。是否可以重写此查询，以便所有工作都在数据库端执行？

代码：

var matches = await
            (from match in _context.Set<Match>()
                let participants = match.Teams
                    .SelectMany(x => x.Participants)
                    .Select(p => new { p.ChampionName, p.Win })
                let teammates = participants.Where(participant => request.TeamChampionNames.Contains(participant.ChampionName))
                let enemies = participants.Where(participant => request.EnemyChampionNames.Contains(participant.ChampionName))
                where teammates.Count() == request.TeamChampionNames.Count()
                      && enemies.Count() == request.EnemyChampionNames.Count()
                select teammates.First().Win // selecting whether teammates win
                )
            .ToListAsync(cancellationToken);

        var winRates = new TeamWinRateResponse
        {
            Wins = matches.Count(hasWon => hasWon),
            Loses = matches.Count(hasWon => !hasWon)
        };

型号：

public record WinRateGetQuery : IRequest<TeamWinRateResponse>
{
    public required IEnumerable<string> TeamChampionNames { get; init; }
    public required IEnumerable<string> EnemyChampionNames { get; init; }
}

public class Match
{
    public string Id { get; set; } = null!;
    
    public virtual ICollection<MatchTeam> Teams { get; set; } = new HashSet<MatchTeam>();
}

public class MatchParticipant
{
    public Guid Id { get; set; }
    public string ChampionName { get; set; } = string.Empty;
    public bool Win { get; set; }

    public string TeamId { get; set; } = null!;
    public virtual MatchTeam Team { get; set; } = null!;
}

public class MatchTeam
{
    public string Id { get; set; } = null!;
    public bool Win { get; set; }

    public string MatchId { get; set; } = null!;
    public virtual Match Match { get; set; } = null!;

    public virtual ICollection<MatchParticipant> Participants { get; set; } = new HashSet<MatchParticipant>();
}

Answer 1

只需将整个事情合并到一个查询中，而不是做

ToListAsync

。

var winRates = (
    from match in _context.Set<Match>()
    let participants = match.Teams
        .SelectMany(x => x.Participants)
        .Select(p => new { p.ChampionName, p.Win })
    let teammates = participants.Where(participant => request.TeamChampionNames.Contains(participant.ChampionName))
    let enemies = participants.Where(participant => request.EnemyChampionNames.Contains(participant.ChampionName))
    where teammates.Count() == request.TeamChampionNames.Count()
       && enemies.Count() == request.EnemyChampionNames.Count()
    select teammates.First().Win // selecting whether teammates win

    group by 1 into matches  // use a constant to do GROUP BY ()
    select new TeamWinRateResponse
    {
        Wins = matches.Count(hasWon => hasWon),
        Loses = matches.Count(hasWon => !hasWon)
    }
).FirstAsync(cancellationToken);