需要帮助创建复杂的EF LINQ选择

Question

Hello i am having some problems creating an complex Linq with multible joins and left joins.

I have 4 tables as listed in the end, what this is used for is to see how i need to send an email about a new reply to a topic. So i fetch all Posts from the topic joined by the user. The same user can ofcause have more then 1 post in each topic. After that i join with UserEmailSetting, this is to see if the user have oped out reciving email notifications. Lastly i need to know if an email have been send to the user notifying about the new reply (I don't want to spam my users if there are made a lot of replys), so if an reply notification have been sendt since the last visit to the site I don't want to send another mail. Here is my try that works, but i would like to optimate it! The problem is that there can be many results on the UserEmailSetting, so i get alot os results back when i infact only get 1 or 2 back.

here is my attept

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();

Here are the database classes

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: a bit more structured layout of what i want the linq to do, I hope It helps

• Get all posts from ForumPostRepository where topicId is 13
• Join with UserRepository on ForumPostRepository.UserId = UserRepository.Id
• Now I only want unike users
• Join with UsersEmailSettingRepository on UserRepository.Id = UsersEmailSettingRepository.UserId
• Left join with EmailLogRepository on UserRepository.Id = EmailLogRepository.UserId AND EmailLogRepository.Type = “ReplyToTopic” AND EmailLogRepository.Values = “topicId”
• -> Now there can be anywhere from 0 to * results on this request, I only want the latest!

Answer 1

No guarantees that this will be performant.

    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;

Signed

A Linq Ninja

edit: just saw that you don't have navigation properties.