Question

在Linq遇到一些问题。我有一个记录列表，如下所示：

var allTeams = new List<AllTeamData>()
{
    new AllTeamData { Team = "Bengals", Conference = "AFC", ConferenceEmail = "AFC@NFL.COM" },
    new AllTeamData { Team = "Steelers", Conference = "AFC", ConferenceEmail = "AFC@NFL.COM" },
    new AllTeamData { Team = "Patriots", Conference = "AFC", ConferenceEmail = "AFC@NFL.COM" },
    new AllTeamData { Team = "Bills", Conference = "AFC", ConferenceEmail = "AFC@NFL.COM" },
    new AllTeamData { Team = "Dolphins", Conference = "AFC", ConferenceEmail = "AFC@NFL.COM" },
    new AllTeamData { Team = "Lions", Conference = "NFC", ConferenceEmail = "NFC@NFL.COM" },
    new AllTeamData { Team = "Bears", Conference = "NFC", ConferenceEmail = "NFC@NFL.COM" },
    new AllTeamData { Team = "Seahawks", Conference = "NFC", ConferenceEmail = "NFC@NFL.COM" },
    new AllTeamData { Team = "Cardinals", Conference = "NFC", ConferenceEmail = "NFC@NFL.COM" },
    new AllTeamData { Team = "Vikings", Conference = "NFC", ConferenceEmail = "NFC@NFL.COM" }
};

我试图做的是以这种形式建立一个记录列表：

public class ConferenceData
{
    public string Conference { get; set; }
    public string ConferenceEmail { get; set; }
    public List<string> Teams { get; set; }
}

我尝试做的是向特定会议电子邮件发送电子邮件，其中包含该特定会议中的团队列表。这是我能用我的linq查询得到的：

var conferences = (from t in allTeams
                           select new ConferenceData
                           {
                               Conference = t.Conference,
                               ConferenceEmail = t.ConferenceEmail
                           }).Distinct().ToList();

希望这一切都有道理。我试图弄清楚我是否需要整理一个嵌套查询来拉动所有团队并将它们放入该对象列表中。不知道该怎么做。任何见解都会很棒。

Answer 1

如果您正在编写SQL查询，那么您将尝试按特定字段对记录进行分组。

同样，LINQ采用GroupBy方法，允许您按会议对数据进行分组：

var conferences = allTeams.GroupBy(t => t.Conference)
                          .Select(grp => new ConferenceData
                                         {
                                             Conference = grp.Key,
                                             ConferenceEmail = grp.First().ConferenceEmail,
                                             Teams = grp.Select(x => x.Team).ToList()
                                         })
                          .ToList();

我已经用方法语法编写了这个，因为这是我更熟悉的内容，但如果您愿意，可以将其翻译为查询语法（类似于您当前的查询）

Answer 2

使用GroupBy或group clause (C# Reference)

var conferences = (from t in allTeams
                  group t by new { t.Conference, t.ConferenceEmail } into g
                  select new ConferenceData {
                      Conference = g.Key.Conference,
                      ConferenceEmail = g.Key.ConferenceEmail,
                      Teams = g.Select(t => t.Team).ToList()
                  }).Tolist();

使用GroupBy

时也是如此

conferences = allTeams.GroupBy(t => new { t.Conference, t.ConferenceEmail })
               .Select(g => new ConferenceData {
                   Conference = g.Key.Conference,
                   ConferenceEmail = g.Key.ConferenceEmail,
                   Teams = g.Select(t => t.Team).ToList()
               }).Tolist();

使用linq根据不同的第二列从一列中选择所有值

2 个答案: