Linq to Entities中的联合订单 [英] Union order in Linq to Entities

问题描述

我对EDM模型联合选择有疑问. 我在数据库中有uniqe ID的记录.例如id列表: 1、2、3、4、5、6、7、8、9

I have a problem with EDM model Union select. I have the records in db with uniqe Ids. For example id list: 1, 2, 3, 4, 5, 6, 7, 8, 9

例如，我需要选择#6记录和#6之前的2条记录以及#6之后的2条记录. 选择结果应为4,5,6,7,8

I need to select, for example, record #6 and 2 records before #6 and 2 records past #6. In select result it should be 4,5,6,7,8

我以另一种方式做

public IQueryable<photos> GetNextPrev(Int64 photoid, string userlogin)
    {
        var p1 = (from m in db.photos
                 where m.id < photoid && m.userlogin == userlogin
                 orderby m.id descending
                 select m).Take(2).Skip(0);
        var p2 = (from m in db.photos
                  where m.id >= photoid && m.userlogin == userlogin
                  orderby m.id descending
                  select m).Take(3).Skip(0);
        return (p1.Union(p2));
    }

但是排序与示例中的不同...

But the ordering is not like in the example...

感谢您的帮助！

推荐答案

这是因为存在后者的联合，所以不能保证它的顺序.您想在退货时这样做:

It's because of the latter Union, you cannot guarantee order with it. You want to do this on your return:

return (p1.Union(p2).OrderByDescending(m => m.id));

更新

对这些问题有进一步的了解后，我认为这将解决该问题:

With further understanding of the issues, I think this will take care of it:

public IQueryable<photos> GetNextPrev(Int64 photoid, string userlogin)
{
    var p1 = (from m in db.photos
             where m.id < photoid && m.userlogin == userlogin
             orderby m.id descending
             select m).Take(2).Skip(0);
    var p2 = (from m in db.photos
              where m.id >= photoid && m.userlogin == userlogin
              orderby m.id 
              select m).Take(3).Skip(0);
    return (p1.Union(p2).OrderBy(m => m.id));
}

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