详细信息使用自定义模型通过LINQ查看相关数据

Posted 2021-04-16

由于我是ASP的新手，确实很困惑如何通过LINQ获得模型/表的某些特定列的列表，反映在相关父项的详细信息页面上。考虑两个类的示例，例如：

public class Tournament
{
    [Key]
    public string TournamentID { get; set; }
    public DateTime TournamentDate { get; set; }
    public string Place { get; set; }

    [ForeignKey("TeamA")]
    public string TeamAID { get; set; }
    public Team TeamA { get; set; }

    [ForeignKey("TeamB")]
    public string TeamBID { get; set; }
    public Team TeamB { get; set; }
}

public class Team
{
    [Key]
    public string TeamID { get; set; }
    public string TeamName { get; set; }
    public string Captain { get; set; }

    [InverseProperty("TeamA")]
    public ICollection<Tournament> TeamA { get; set; }

    [InverseProperty("TeamB")]
    public ICollection<Tournament> TeamB { get; set; }
}

这两个表格包含了团队的详细信息，以及他们之间的锦标赛。由于锦标赛的模型/表格不止一个领域与团队相关联，因此正在使用InverseProperty和相关的ForeignKeys。

主要目标是在视图中呈现顶部团队的一部分细节，但下面列出的锦标赛的相关条目相同。

由于团队（例如Team_1）可能存在于锦标赛的TeamA列中，甚至存在于TeamB列中，因此会弹出如何以下列方式呈现相同内容的问题：

TeamID：ID_1

TeamName：Team_1

TeamCaptain：队长1

ID |日期|竞争对手|地点

.... | ........ | ................ | .........

.... | ........ | ................ | .........

出于同样的原因，我推断出我应该为Custom Columns使用一些特殊的Model Class，因此添加了以下类：

public class GamesList
{
    public string TID { get; set; }
    public DateTime TDate { get; set; }
    public string TPlace { get; set; }
    public string TeamLinks { get; set; }
    public string TeamNames { get; set; }
}

和控制器动作如：

    public async Task<IActionResult> Index2(string teamId)
    {
        var gamesList = ((from x in _context.Tournaments
                                .Where(x => x.TeamAID == teamId)
                                select new GamesList
                                {
                                    TID = x.TournamentID,
                                    TDate = x.TournamentDate,
                                    TeamLinks = x.TeamAID,
                                    TeamNames = x.TeamB.TeamName,
                                    TPlace = x.Place
                                })
                        .Concat(from x in _context.Tournaments
                                .Where(x => x.TeamBID == teamId)
                                select new GamesList
                                {
                                    TID = x.TournamentID,
                                    TDate = x.TournamentDate,
                                    TeamLinks = x.TeamBID,
                                    TeamNames = x.TeamA.TeamName,
                                    TPlace = x.Place
                                })).OrderBy(x => x.TDate);

        return View(await gamesList.ToListAsync());
    }

因此，要将相同的列表连接起来，但是团队ID和名称被翻转，导致所有ID都在名为TeamLinks的属性中编译，而竞争对手的名称在TeamNames中排列。

现在，所述列表可以通过拥有@model IEnumerable来呈现，但是作为主要目标指定了如何在团队的详细信息下呈现这样的列表（即也拥有TeamID == teamId的那个）？

谢谢。

答案

您需要从表示视图中所需内容的视图模型开始

public class TeamVM
{
    public string ID { get; set; }
    public string Name { get; set; }
    public string Captain { get; set; }
    public IEnumerable<TournamentVM> Tournaments { get; set; }
}
public class TournamentVM
{
    public string ID { get; set; }
    public DateTime Date { get; set; }
    public string Place { get; set; }
    public string Competitor { get; set; }
}

然后查询您的数据库以获得团队（通过其TeamID），包括Tournament的集合，并将结果映射到您的视图模型。使用LinqToEntities

Team team = db.Teams.Where(x => x.TeamID == teamId).FirstOrDefault();
if (team == null) { ... }; // error

TeamVM model = new TeamVM
{
    ID = team.TeamID,
    Name = team.TeamName,
    Captain = team.Captain,
    // join the collections into a new collection of TournamentVM
    Tournaments = team.TeamA.Where(x => x.TeamAID == team.TeamID).Select(x => new TournamentVM
    {
        ID = x.TournamentID,
        Date = x.TournamentDate,
        Place = x.Place,
        Competitor = x.TeamB.TeamName
    }).Concat(team.TeamB.Where(x => x.TeamBID == team.TeamID).Select(x => new TournamentVM
    {
        ID = x.TournamentID,
        Date = x.TournamentDate,
        Place = x.Place,
        Competitor = x.TeamA.TeamName
    })).OrderBy(x => x.Date)
};
return View(model);

并在视图中

@model TeamVM
....
<div>@Model.ID</div>
....
<table>
   <thead> ... </thead>
   <tbody>
       @foreach(var item in Model.Tournaments)
       {
           <tr>
               <td>@item.ID</td>
               <td>@item.Date</td>
               ....
           </tr>
       }
    </tbody>
</table>