linq inner join

var id = 1;
var query =
   from post in database.Posts
   join meta in database.Post_Metas on post.ID equals meta.Post_ID
   where post.ID == id
   select new { Post = post, Meta = meta };

from t1 in db.Table1
join t2 in db.Table2 on t1.field equals t2.field
select new { t1.field2, t2.field3}