Question

我正在编写一个应用程序，允许我们的用户向他们的联系人发送简报。这是数据库结构（仅限重要字段）：

Contacts(tbl)       ContactEmails(tbl)       Newsletters(tbl)
  ContactID           ContactEmailID           NewsletterID
  ...                 ContactID (fk)           ...
                      EmailAddress             
                      Deleted
                      ...


NewsletterLists(tbl)       NewsletterToLists(tbl)
  NewsletterListID           NewsletterID (fk)
  ...                        NewsletterListID (fk)


NewsletterListToContacts(tbl)
  NewsletterListID (fk)
  ContactID (fk)
  Active
  Deleted
  UnsubscribedOn
  ...

现在我的课程结构为：

public class NewsletterContactEmails
{
    public int ContactID { get; set; }
    public List<string> EmailList { get; set; }
}

我希望每个联系人都有一个NewsletterContactEmails对象，以便我可以遍历它并为每个联系人发送一封电子邮件（而不是每个电子邮件地址）。

我有新闻稿对象开始使用。所以在伪中它会......

1. Get NewsletterLists this newsletter is to send to.
2. Get Active (double opted-in) and non-deleted/unsubscribed DISTINCT Contact List from said NewsletterLists.
3. Create NewsletterContactEmails object for each contact and add their non-deleted DISTINCT list of email addresses.

我想在一个查询中执行此操作。这是我现在拥有的，我认为我很接近，但这甚至不会编译：

List<NewsletterContactEmails> Recipients = objNewsletter.NewsletterToLists
                    .Select(ntl => ntl.NewsletterList.NewsletterListToContacts
                        .Where(nl => nl.Active == true && nl.Deleted == false && nl.UnsubscribedOn == null)
                        .Select(nl => new NewsletterContactEmails {
                            ContactID = nl.ContactID,
                            EmailList = nl.Contact.ContactEmails.Where(ce => ce.Deleted == false).Select(ce => ce.EmailAddress).Distinct().ToList()
                        }));

非常感谢任何帮助！

Answer 1

List<NewsletterContactEmails> Recipients = objNewsletter.NewsletterToLists
    .SelectMany(ntl => ntl.NewsletterList.NewsletterListToContacts
        .Where(nl => nl.Active == true && nl.Deleted == false && nl.UnsubscribedOn == null)
        .Select(nl => new NewsletterContactEmails
        {
            ContactID = nl.ContactID,
            EmailList =
                nl.Contact.ContactEmails.Where(ce => ce.Deleted == false)
                    .Select(ce => ce.EmailAddress)
                    .Distinct()
                    .ToList()
        }));

首先选择SelectMany而不是Select

如何编写这个复杂的LINQ to Entities查询

1 个答案: