不相关实体变量的 Linq 子查询

Question

是否可以使用 Linq convert/duplicate 以下内容？

DECLARE @UserID INT = 1, @ViewerUserID INT = 1002;

SELECT UGR.*,
CASE
WHEN (
    SELECT subR.[Level]
    FROM UserGameRanks subUGR WITH (NOLOCK)
    INNER JOIN Ranks subR WITH (NOLOCK) ON (subUGR.RankId = subR.Id)
    INNER JOIN Games subG WITH (NOLOCK) ON (subUGR.GameId = subG.Id)
    INNER JOIN Users subU WITH (NOLOCK) ON (subUGR.UserID = subU.Id)
    WHERE subUGR.IsDeleted = 0 AND subU.Id = @ViewerUserID AND subUGR.GameID = UGR.GameId
) > R.[Level] THEN 1
ELSE 0
END AS CanEdit
FROM UserGameRanks UGR WITH (NOLOCK)
INNER JOIN Ranks R WITH (NOLOCK) ON (UGR.RankId = R.Id)
INNER JOIN Games G WITH (NOLOCK) ON (UGR.GameId = G.Id)
INNER JOIN Users U WITH (NOLOCK) ON (UGR.UserID = U.Id)
WHERE UGR.IsDeleted = 0 AND U.Id = @UserID
AND
(
    (
        (@ViewerUserID <> - 1)
        AND
        (UGR.VisibilityId = 1)
    )
    OR
    (
        (UGR.VisibilityId = 2)
    )
    OR
    (
        (UGR.VisibilityId = 0)
        AND
        (@UserID = @ViewerUserID)
    )
)

特别是 CASE 子查询？我向用户实体 class 添加了一个 [NotMapped] CanEdit 值，但是我不确定如何用一个 sql 查询填充它，而不是先执行初始获取，然后循环遍历并更新 CanEdit .

我浏览了 Whosebug。

如有任何帮助，我们将不胜感激。

编辑：看了你的回答，我明白了怎么做，但我意识到我在问题中编造了一个东西。我最初创建上述查询作为我的问题的示例，但我现在发现它与我的问题没有直接关系。我更新了 SQL 部分...

我们的想法是，我们可能有很多排名，最低排名是 "Unset"，这将是级别 0。所以如果我玩另一个用户玩的游戏并且我的排名设置在级别 2，我可以将此用户的排名分配给 1。但在不同的游戏中，我也可能是 "Unset"（级别 0），因此无法编辑 his/her 排名。

@CodingYoshi：这是我尝试过的

var viewerQuery = from ugr in context.UserGameRanks
                               join r in context.Ranks on ugr.RankId equals r.Id
                               join g in context.Games on ugr.GameId equals g.Id
                               join u in context.Users on ugr.UserId equals u.Id
                               where (!ugr.IsDeleted) && (ugr.UserId == viewerUserId)
                               select new { UserGameRank = ugr };

            var query = from ugr in context.UserGameRanks
                        join r in context.Ranks on ugr.RankId equals r.Id
                        join g in context.Games on ugr.GameId equals g.Id
                        join u in context.Users on ugr.UserId equals u.Id
                        where (!ugr.IsDeleted) && (ugr.UserId == userId) &&
                        (
                            (viewerUserId != -1 && ugr.VisibilityId == Visibility.RegisteredUsers)
                            ||
                            (ugr.VisibilityId == Visibility.Public)
                            ||
                            (ugr.VisibilityId == Visibility.Hidden && userId == viewerUserId)
                        )
                        select new { GameName = g.Name, Username = ugr.Username, RankName = r.Name, CanEdit = (viewerQuery.Rank.Level > r.Level ? 1 : 0) };

Answer 1

也许是这样的：

var users = new List<User>
{
    new User { Id = 1, UserName = "User1", UserTypeId = 1 }, 
    new User { Id = 2, UserName = "User2", UserTypeId = 2 }, 
    new User { Id = 3, UserName = "User3", UserTypeId = 2 }, 
};

var userTypes = new List<UserType>
{
    new UserType { Id = 1, Type = "Admin", Security = 1 }, 
    new UserType { Id = 2, Type = "User", Security = 2  }
};

var userId = 1;

var ViewerUserID = 2;
var viewerSecurity = 
    (from u in users
    join ut in userTypes on u.UserTypeId equals ut.Id
    where u.Id == ViewerUserID
    select ut.Security).FirstOrDefault();

var res = 
    (from u in users
    join ut in userTypes on u.UserTypeId equals ut.Id
    where u.Id == userId || u.Id == -1
    select new
    {
        Id = u.Id,
        UserName = u.UserName,
        CanEdit = viewerSecurity > ut.Security ? 1 : 0
    });
}

class User {
    public int Id {get; set;}
    public string UserName {get; set;}
    public int UserTypeId {get; set;}
}

class UserType {
    public int Id {get; set;}
    public string Type {get; set;}
    public int Security {get; set;}
}

更新： 首先，无需编辑您的问题，因为其他人回答了您最初的问题，现在他们和我的最初回答毫无意义。 你应该开始一个新问题或更新这个问题。

这是您编辑的问题的代码：

var res = 
    (from ugr in userGameRanks
    join r in ranks on ugr.RankId equals r.Id
    join g in games on ugr.GameId equals g.Id
    join u in users on ugr.UserId equals u.Id
    where !ugr.IsDeleted    // assuming IsDeleted is of type BIT in your DB
        && u.Id == userId
        && (
                (ViewerUserID != -1 && ugr.VisibilityId == 1)
                || ugr.VisibilityId == 2
                || (ugr.VisibilityId == 0 && userId == ViewerUserID)
            )
    let level =
        (from subUGR in userGameRanks
        join subR in ranks on subUGR.RankId equals subR.Id
        join subG in games on subUGR.GameId equals subG.Id
        join subU in users on subUGR.UserId equals subU.Id
        where !subUGR.IsDeleted 
            && subU.Id == ViewerUserID
            && subUGR.GameId == ugr.GameId
        select subR.Level).FirstOrDefault()

    select new 
    {
        ugr.RankId, 
        ugr.UserId,
        ugr.GameId,
        ugr.IsDeleted,
        ugr.VisibilityId,
        CanEdit = level > r.Level ? 1 : 0
    });

希望对您有所帮助

Answer 2

我将数据库建模为类以使语法正确。不确定我是否做对了一切，但已经很接近了

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            int UserID = 1;
            int ViewerUserID = 2;

            DataBase db = new DataBase();

            var resutls = (from subU in db.subU
                           join subUt in db.subUT on subU.Id equals subUt.UserTypeID
                           select new { subU = subU, subUt = subUt })
                           .Where(x => ((x.subU.Id == ViewerUserID) && (x.subUt.Security > x.subU.Security)) || x.subU.Id == -1)
                           .ToList();
        }
    }
    public class DataBase
    {
        public List<Users> subU { get; set; }
        public List<UserTypes> subUT { get; set; }

    }
    public class Users
    {
        public int Id { get; set; }
        public int Security { get; set; }
    }
    public class UserTypes
    {
        public int UserTypeID { get; set; }
        public int Security { get; set; }
    }
}

Answer 3

几个问题：

1) 所有联接有什么用？您应该在模型配置中正确设置导航属性。

2) 结果查询的 CanEdit 属性依赖于指定 viewerUserId 的游戏等级，但似乎指定 viewerUserId 是可选的。如果未指定或未找到查看器用户，默认行为是什么？我假设 CanEdit 应该是错误的。

public class YourResultClass()
{
    public string GameName { get; set; }
    public string UserName { get; set; }
    public string RankName { get; set; }
    public bool CanEdit { get; set; }
}

var targetUserGameRanksQuery = context.Users
    .Where(u => !u.IsDeleted 
        && u.UserId == userId)
    // flatten for use in subsequent join
    .SelectMany(u => u.UserGameRanks);

IQueryable<YourResultClass> query = null;

if(viewerUserId.HasValue)
{
    var viewerGameRanksQuery = context.Users
        .Where(u => !u.IsDeleted 
            && u.UserId == viewerUserId)
        // flatten for use in subsequent join
        .SelectMany(u => u.UserGameRanks);

    var joinQuery = targetUserGameRanksQuery // outer source `o`
        .Join(viewerGameRanksQuery, // inner source `i`
            o => o.GameId,
            i => i.GameId,
            (o, i) => new
            {
                GameName = o.Game.Name,
                TargetUserName = o.Username,
                TargetRankName = o.Rank.Name,
                CanEdit = i.Rank.Level > o.Rank.Level,
                Visibility = o.VisibilityId
            });

    query = joinQuery
        .Where(at =>
            at.Visibility == Visibility.RegisteredUsers

            || (at.Visibility == Visibility.Hidden
                && userId == viewerUserId.Value)

            || at.Visibility == Visibility.Public )
        .Select(at =>
            new YourResultClass()
            {
                GameName = at.GameName,
                UserName = at.UserName,
                RankName = at.RankName,
                CanEdit = at.CanEdit,
            });
}
else
{
    query = targetUserGameRanksQuery
        .Where(ugh => ugr.VisibilityId == Visibility.Public)
        .Select(ugh => new YourResultClass()
        {
            GameName = ugr.Game.Name,
            UserName = ugr.Username,
            RankName = ugr.Rank.Name,
            CanEdit = false,
        });
}

不相关实体变量的 Linq 子查询

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