1

使用 Linq 和 EF

一个User可以有很多RoleUserLinks。

如果 aUser的RoleUserLink表包含 2 条记录 - 一条具有 a LinkStatusIDof Deleted，一条具有 a LinkStatusIDof Added，则下面的查询将返回User。我不想要这个。

如何不返回user如果有任何关联LinkStatusID的，Added请参阅下面的案例 3

IEnumerable<User> z =
    (from users in listOfUsersForReviewer
     join roleUserLinks in context.RoleUserLinks
        on users.UserID equals roleUserLinks.UserID into roleUserLinksJoin
     // left join
     from roleUserLinks in roleUserLinksJoin.DefaultIfEmpty()
     where
         // case 1 - has never been added to a role ie record isn't there
         roleUserLinks.LinkStatus == null
         // case 2 - has been soft deleted from a role so we want this record
         || roleUserLinks.LinkStatusID == (byte)Enums.LinkStatus.Deleted
     select users).Distinct();

案例 1) 用户没有关联RoleUserLink记录。用户按预期返回

案例 2) 用户有 1 条关联RoleUserLink记录与LinkStatusID已删除。用户按预期返回

案例 3) 用户有 2 条关联RoleUserLink记录。1 有一个LinkStatusID已删除。用户不应该被退回

4

2 回答 2

1

如果我理解得很好，它应该是：

IEnumerable<User> z =
    (from users in listOfUsersForReviewer
     join roleUserLinks in context.RoleUserLinks
        on users.UserID equals roleUserLinks.UserID into roleUserLinksJoin
     // left join
     from roleUserLinks in roleUserLinksJoin.DefaultIfEmpty()
     where
         (roleUserLinks == null
         || roleUserLinks.LinkStatusID == (byte)Enums.LinkStatus.Deleted)
         && !roleUserLinksJoin.Where(x=> roleUserLinks.LinkStatusID == (byte)Enums.LinkStatus.Added && x.UserID == roleUserLinks.UserID).Any()
     select users).Distinct();

我添加了这个子查询：

&& !roleUserLinksJoin.Where(x=> roleUserLinks.LinkStatusID == (byte)Enums.LinkStatus.Added && x.UserID == roleUserLinks.UserID).Any()

它将从结果中删除不需要的行，其中包含有记录的RoleUserLinks用户LinkStatusId Added。

我也将其更改roleUserLinks.LinkStatus == null为roleUserLinks == null避免NullReferenceException在没有匹配的情况RoleUserLink下User

我测试代码的示例代码

static void Main(string[] args)
{
    var usersList = new List<User>()
                    {
                        new User() {UserID = 1},
                        new User() {UserID = 2},
                        new User() {UserID = 3}
                    };

    var userLinksList = new List<RoleUserLink>()
                        {
                            new RoleUserLink() {UserID = 1, State = "del"},
                            new RoleUserLink() {UserID = 2, State = "add"},
                            new RoleUserLink() {UserID = 2, State = "del"}
                        };

    IEnumerable<User> z = (from users in usersList 
                           join roleUserLinks in userLinksList
                           on users.UserID equals roleUserLinks.UserID into roleUserLinksJoin
                           // left join
                           from roleUserLinks in roleUserLinksJoin.DefaultIfEmpty()
                           where
                            // has never been added to a role ie record isn't there
                                roleUserLinks == null
                            // has been soft deleted from a role so we want this record
                                || roleUserLinks.State == "del"
                            // has been added to role so we don't want this record
                                && !roleUserLinksJoin.Where(x=> x.State == "add" && x.UserID == roleUserLinks.UserID).Any()
                            select users).Distinct();
    var res = z.ToList();

}

public class User
{
    public int UserID { get; set; }
}

public class RoleUserLink
{
    public int UserID { get; set; }
    public string State { get; set; }
}

它返回 id 为 1 和 3 的用户。正如我所料。UserId:1仅与 status 有联系delete。UserId:3没有任何链接。并且UserId:2不会返回，因为它也与 status 链接add。

于 2013-01-08T12:56:19.077 回答
0

我通过原始查询解决了这个问题：

IEnumerable<User> z =
    (from users in listOfUsersForReviewer
     join roleUserLinks in context.RoleUserLinks
        on users.UserID equals roleUserLinks.UserID into roleUserLinksJoin
     // left join
     from roleUserLinks in roleUserLinksJoin.DefaultIfEmpty()
     where
         // case 1 - has never been added to a role ie record isn't there
         roleUserLinks.LinkStatus == null
         // case 2 - has been soft deleted from a role so we want this record
         || roleUserLinks.LinkStatusID == (byte)Enums.LinkStatus.Deleted
     select users).Distinct().Include(b => b.RoleUserLinks).ToList();

并在最后添加了 Include 和 ToList。

然后：

var list = new List<User>();

    foreach (var user in z)
    {
        bool shouldReturnUser = true;
        //get roleLinks
        foreach (var rul in user.RoleUserLinks)
        {
            if (rul.LinkStatusID == (byte) Enums.LinkStatus.Added)
                shouldReturnUser = false;
        }
        if (shouldReturnUser)
            list.Add(user);
    }

然后返回此列表。

我知道这样做会产生性能影响，并在网络服务器上进行处理，但恕我直言，这很容易理解，并且有效:-)

于 2013-01-08T17:21:54.180 回答