c# – 需要帮助创建复杂的ef linq选择

2023年4月7日 117次阅读

你好,我在创建一个复杂的
Linq与多个连接和左连接时遇到了一些问题.

我最后列出了4个表,这用于查看我如何发送有关主题的新回复的电子邮件.所以我从用户加入的主题中获取所有帖子.同一个用户可以在每个主题中有超过1个帖子.
之后,我加入UserEmailSetting,这是为了查看用户是否已经打开了收到的电子邮件通知.最后,我需要知道是否已向用户发送了一封电子邮件,通知新回复(如果有大量回复,我不想向我的用户发送垃圾邮件),所以如果回复通知自上次发送以来访问该网站我不想再发送邮件.这是我的尝试,但我想优先考虑！
问题是UserEmailSetting上可能会有很多结果,所以当我实际上只得到1或2时,我会得到很多os结果.

这是我的经历

var select = (from p in ForumPostRepository.Get()
              join u in UserRepository.Get() on p.UserId equals u.Id
              join ues in UsersEmailSettingRepository.Get() on u.Id equals ues.UserId

              join els in
                  (from _el in EmailLogRepository.Get()
                   where _el.Type == "ReplyToTopic" &&
                             _el.Values == topicId
                       orderby _el.Id descending 
                       select _el) on u.Id equals els.UserId 
                        into emailLogs

              from el in emailLogs.DefaultIfEmpty()

              where p.TopicId == forumTopic.Id &&
                    ues.ReplyToTopic //&& // We only want people who need notifications
                    //!u.Online // We only want people who are not online

              orderby p.Id descending, el.Id descending
              select new
              {
                  User = u,
                  EmailLog = el
              });

    var result = select.DistinctBy(x => x.User.Id).ToList();

这是数据库类

public class ForumPost
{
    public int? TopicId { get; set; }
    public int UserId { get; set; }
    ...
}

public class User
{
    public int Id { get; set; }
    public bool Online { get; set; }
    public DateTime LastLogin { get; set; }
    ...
}

public class UsersEmailSetting
{
    public int UserId { get; set; }
    public bool ReplyToTopic { get; set; }
}

public class EmailLog
{
    public int Id { get; set; }
    public int UserId { get; set; }
    public string Type { get; set; }
    public string Values { get; set; }
    public DateTime Created { get; set; }
}

Updata：我希望linq做的更有条理的布局,我希望它有所帮助

>从ForumPostRepository获取所有帖子,其中topicId为13
>在ForumPostRepository.UserId = UserRepository.Id上加入UserRepository
>现在我只想要不受欢迎的用户
>在UserRepository.Id =上加入UsersEmailSettingRepository
UsersEmailSettingRepository.UserId
>在UserRepository.Id =上与EmailLogRepository进行左连接
EmailLogRepository.UserId和EmailLogRepository.Type =
“ReplyToTopic”和EmailLogRepository.Values =“topicId”
> – >现在这个请求可以有从0到*的结果,我只想要最新的！

最佳答案 不保证这将是高效的.

    var users = UserRepository.Get();
    var userEmailSettings = UsersEmailSettingRepository.Get();
    var emailLogs = EmailLogRepository.Get();
    var posts = ForumPostRepository.Get();
    var foo = 
        from user in users
        where posts
               .Any(post => post.UserId == u.Id && post.TopicId == topicId)
        where userEmailSettings
               .Any(ues => u.Id equals ues.UserId && ues.ReplyToTopic == true)
        where false == 
        (
                from el in emailLogs
                where el.Type == "ReplyToTopic"
                && el.Values == topicId
                && el.UserId == user.Id
                && el.Created > user.LastLogin
                select el
        ).Any()
        select user;

签

一个Linq Ninja

编辑：刚看到你没有导航属性.

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