EF的连表查询Lambda表达式和linq语句
var lst = from c in db.Blogs join p in db.Posts on c.Id equals p.BlogId where p.Id==1 select c;
var lst1 = db.Blogs.Join(db.Posts.Where(p=>p.Id==1), b=> b.Id, p=> p.BlogId, (b, p) => new {b});
public class Blog
{
public int Id { get; set; }
public string Title { get; set; }
}
public class Post
{
public int Id { get; set; }
public string Title { get; set; }
public int BlogId { get; set; }
}
public List<CommentsViewModel> GetCommentsByPid(int pid, int uid)
{
var query = from a in db.Photos
join b in db.Comments on a.PID equals b.PID
join c in db.Users on b.UID equals c.UID
where a.PID == pid
select new CommentsViewModel { Id = b.ID, Author = c.UserName, Comment = b.Content, UserAvatar = c.HeadPic, CanDelete = uid == b.UID ? true : false, CanReplay = true, TempDate = b.CreateTime, ParentId = b.ParentId };
var ret = query.ToList();
return ret;
//或者
var data = db.Photos.
Join(db.Comments, p => p.PID, c => c.PID,
(p, c) => new { p, c }).
Join(db.Users, n => n.c.UID, u => u.UID, (n, u) => new { n, u })
.Where(m => m.n.p.PID == pid)
.Select(m => new CommentsViewModel
{
Id = m.n.c.ID,
Author = m.u.UserName,
Comment =m.n.c.Content,
});
return data.ToList();
}
var lst = from c in db.Blogs join p in db.Posts on c.Id equals p.BlogId where p.Id==1 select c;
var lst1 = db.Blogs.Join(db.Posts.Where(p=>p.Id==1), b=> b.Id, p=> p.BlogId, (b, p) => new {b});
public class Blog
{
public int Id { get; set; }
public string Title { get; set; }
}
public class Post
{
public int Id { get; set; }
public string Title { get; set; }
public int BlogId { get; set; }
}
public List<CommentsViewModel> GetCommentsByPid(int pid, int uid)
{
var query = from a in db.Photos
join b in db.Comments on a.PID equals b.PID
join c in db.Users on b.UID equals c.UID
where a.PID == pid
select new CommentsViewModel { Id = b.ID, Author = c.UserName, Comment = b.Content, UserAvatar = c.HeadPic, CanDelete = uid == b.UID ? true : false, CanReplay = true, TempDate = b.CreateTime, ParentId = b.ParentId };
var ret = query.ToList();
return ret;
//或者
var data = db.Photos.
Join(db.Comments, p => p.PID, c => c.PID,
(p, c) => new { p, c }).
Join(db.Users, n => n.c.UID, u => u.UID, (n, u) => new { n, u })
.Where(m => m.n.p.PID == pid)
.Select(m => new CommentsViewModel
{
Id = m.n.c.ID,
Author = m.u.UserName,
Comment =m.n.c.Content,
});
return data.ToList();
}