Question

我有PM收件箱和2个表：用户和管理员。

我有这个问题：

            return (from pm in dc.PrivateMessages
                   join user in dc.Users
                   on pm.Sender equals user.UserID
                   select new PMInbox
                                 {
                                     SenderUsername = user.Username
                                 }).ToList();

但我只能拥有来自用户发件人的所有PM。

我必须在这里添加哪种联接才能拥有pm.Sender == user.UserID或pm.Sender == admin.AdminID？

Answer 1

从逻辑上讲，这就是：

var messageUsers = dc.PrivateMessages.Join(dc.Users,
                                           pm => pm.Sender,
                                           user => user.UserId,
                                           (pm, user) => user);
var messageAdmins = dc.PrivateMessages.Join(dc.Users,
                                           pm => pm.Sender,
                                           admin => admin.AdminID,
                                           (pm, admin) => admin);
return messageUsers.Union(messageAdmins)
                   .Select(user => new PMInbox {
                       SenderUsername = user.Username
                    })
                   .ToList();

或者你可以使其成为与where子句的交叉连接：

return (from pm in dc.PrivateMessages
        from user in dc.Users
        where pm.Sender == user.UserID || pm.Sender == user.AdminID
        select new PMInbox
        {
            SenderUsername = user.Username
        }).ToList();

哪个加入LINQ？

1 个答案: