Question

我正在使用linq来实现sql。我正在运行一个查询，它使用一个函数来返回正确的记录。我正在使用一个函数，所以我可以使用if语句，我不知道如何在linq子句中做到这一点。代码复制如下。它返回一个错误：＆＃34; GetPageOwner（int 32）没有支持的转换为sql＆＃34;我究竟做错了什么？如何解决它以获得相同的结果？

   return (from page select new Result
        {

            pageOwner = GetPageOwner(page.page_id)
        });


    public Post GetPageOwner(int pageid)
    {

        var posts = (from dp in db.Posts where dp.pageid == pageid select dp);
        var returned = posts;

        if (posts.Count() > 0)
        {
            var latest = posts.OrderByDescending(o => o.Date).FirstOrDefault();
            var sharedsamedayaslatest = (from p in posts where p.Date.AddDays(1) >= latest.Date select p);
            if (sharedsamedayaslatest.Count() > 1)
            {
                var followedpost = (from p in posts from s in db.Subscriptions where s.Subscriber == UID && s.Subscribedto == p.UserId select p);
                var count = followedpost.Count();
                if (count == 1)
                {
                    returned = followedpost;
                }
                else if (count > 1)
                {
                    returned = (from s in followedpost let reposts = GetPostReposts(s.id) let rating = GetPostRating(s.id) let score = reposts + rating orderby score descending select s);
                }
                else
                { 
                    //no follower shared this post so return the most liked
                    returned = (from s in sharedsamedayaslatest let reposts = GetPostReposts(s.id) let rating = GetPostRating(s.id) let score = reposts + rating orderby score descending select s);
                }
            }
            else
            {
                //no shares on the day the latest share
                returned = sharedsamedayaslatest;
            }
        }
        else
        {
            //only one post
            returned = posts;
        }


        return returned.FirstOrDefault(); //order by userid gets a random one



    }

Answer 1

Linq to sql必须将.net中的函数转换为sql。并非所有.net函数都在sql中具有等效函数，而且由您编写的函数肯定没有。

话虽如此，您可以将您的函数实现为存储过程，并在您的linq查询中使用它。

没有支持的转换为SQL错误？

1 个答案: