Question

我有3个名为Posts，Tags和PostXTags的表，PostXTags是帖子和标签之间的连接器。

我尝试在linq中进行以下查询但是我从未实现过理想的结果。

请帮我写一下这个查询的正确linq：

SELECT * FROM Posts
INNER JOIN PostXTags
ON Posts.PostID = PostXTags.PostID
LEFT JOIN Tags
ON PostXTags.TagID = Tags.TagID

Answer 1

var query = from p in Posts
            join x in PostXTags on p.PostID equals x.PostID
            join t in Tags on x.TagID equals t.TagID into joinedTags
            from t in joinedTags.DefaultIfEmpty()  //left join                
            select new { Posts = p, Tags = t };    //t could be null

Answer 2

我想你想实现这个目标：

var query = context.Tags.Where(t => t.Id == id).SelectMany(t => t.Posts);

linq查询内连接和左连接的问题

2 个答案: