c# - 如何将行按特定顺序保存到 ASP .NET 中的关联实体中？

Question

我正在创建一个可以注册玩游戏的玩家的系统。一场游戏最多可以有4名玩家，玩家可以无限次玩游戏。相关源码:

    public class Player
{
    public int PlayerId { get; set; }

    [Required]
    public string Username { get; set; }

    public virtual ICollection<Game> Games { get; set; }
}

并且:

 public class Game
    {
        public int GameId { get; set; }

        [Required]
        public string Location { get; set; }

        public virtual ICollection<Player> Players { get; set; }
    }

EF 正确生成了这些表，并且还生成了一个额外的表:PlayerGames，它有两列:Player_PlayerId 和 Game_GameId。它看起来像这样:http://imgur.com/AGdKN3P

GamesController 的 Create 方法如下所示:

   public ActionResult Create([Bind(Include = "GameId,Location,PlayerId")] Game game)
    {
            int[] ids = Request.Form["PlayerId"].Split(',').Select(Int32.Parse).ToArray();
            List<Player> k = ids.Select(t => db.Players.First(x => x.PlayerId == t)).ToList();
            ICollection<Player> players = ids.Select(t => db.Players.First(x => x.PlayerId == t)).ToList();
            game.Players = players;

            db.Database.Log = s => Debug.Write(s);
            if (ModelState.IsValid)
            {
                db.Games.Add(game);
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(game);
    }

问题在于 db.SaveChanges() 生成的查询忽略了玩家列表的顺序:Id-s 每次都会按顺序排列。然而，对于系统来说，了解玩家在列表中的顺序非常重要。有什么方法可以将其插入数据库并保留顺序吗？

以下是SQL日志供引用:

INSERT [dbo].[PlayerGames]([Player_PlayerId], [Game_GameId])
VALUES (@0, @1)
-- @0: '2' (Type = Int32)
-- @1: '1013' (Type = Int32)
-- Executing at 4/21/2015 1:22:13 PM +02:00
-- Completed in 1 ms with result: 1

INSERT [dbo].[PlayerGames]([Player_PlayerId], [Game_GameId])
VALUES (@0, @1)
-- @0: '3' (Type = Int32)
-- @1: '1013' (Type = Int32)

-- Executing at 4/21/2015 1:22:13 PM +02:00
-- Completed in 0 ms with result: 1

INSERT [dbo].[PlayerGames]([Player_PlayerId], [Game_GameId])
VALUES (@0, @1)
-- @0: '4' (Type = Int32)
-- @1: '1013' (Type = Int32)
-- Executing at 4/21/2015 1:22:13 PM +02:00
-- Completed in 0 ms with result: 1

INSERT [dbo].[PlayerGames]([Player_PlayerId], [Game_GameId])
VALUES (@0, @1)
-- @0: '6' (Type = Int32)
-- @1: '1013' (Type = Int32)
-- Executing at 4/21/2015 1:22:13 PM +02:00
-- Completed in 0 ms with result: 1

Answer 1

你的类应该是这样的:

public class Player
{
    public int PlayerId { get; set; }
    [Required]
    public string Username { get; set; }
    public virtual ICollection<OpenedGame> OpenedGames { get; set; }
}

public class Game
{
    public int GameId { get; set; }
    [Required]
    public string Location { get; set; }
    public virtual ICollection<OpenedGame> OpenedGames { get; set; }
}

public class OpenedGame
{
    public int OpenedGameId { get; set; }
    public int GameId { get; set; }
    public virtual Game Game { get; set; }
    public int PlayerId { get; set; }
    public virtual Player Player { get; set; }
    public int Location { get; set; }
}

这样您就可以跟踪哪个玩家在游戏中的哪个位置。

编辑:如果您想检查玩家正在玩什么游戏，请执行以下操作:

var list = context.OpenedGames.Where(x=>x.PlayerId==pId).ToList();

或玩单一游戏的玩家列表:

var list = context.OpenedGames.Where(x=>x.GameId==gId).ToList();