LINQ查询联接 [英] LINQ query Joins

问题描述

When i use the below code to retrieve information, it shows an error..

var mails = from m in entity.mailboxes
            join p in entity.ordinary_user_profile_info on m.from_id equals p.user_id
            select new MailList
            {
                mid = m.m_id,
                mfrom = m.**from_id,** // Error occours here
                mfomname = p.username,
                msubject = m.subject
            };

错误是：

Error is:

int？mailbox.from_id

"int? mailbox.from_id "

不能将类型'int？'隐式转换为'int'。显式转换存在（您是否缺少演员？）

Cannot implicitly convert type 'int?' to 'int'. An explicit conversion exists (are you missing a cast?)

我声明了 m_id 和 from_id 作为数据库中的int以及MailList类中的数据。

I have declared m_id and from_id as int in DB as well as in MailList class.

推荐答案

var mails = from m in entity.mailboxes
            join p in entity.ordinary_user_profile_info on m.from_id equals p.user_id
            select new MailList
            {
                mid = m.m_id,
                mfrom = m.from_id ?? 0,
                mfomname = p.username,
                msubject = m.subject
            };

这篇关于LINQ查询联接的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！