Question

可能重复：
Conditional “orderby” sort order in LINQ

请告诉我如何使用不同的列对以下查询进行排序，具体取决于条件，例如现在它按OfferID降序排序，

var myoffer = (from b in MMEntities.OfferDisplays.AsExpandable().Where(pred)
                       where b.Offers.Accounts.AccountID == accountID && b.Offers.OfferID != 0  && !((from bb in MMEntities.OfferDisplays.AsExpandable().Where(pred)
                             where
                               bb.Offers.Accounts.AccountID == accountID && bb.Offers.OfferID != 0  orderby
                             bb.Offers.OfferID descending
                             select new
                             {
                                 bb.Offers.OfferID
                             }).Take(10)).Contains(new { b.Offers.OfferID }) &&
                         b.Offers.Accounts.AccountID == accountID orderby
                         b.Offers.OfferID descending

Answer 1

你可以用吗？：`OrderBy'语句中的：运算符

如果条件为真，则

condition ? value1 : value2评估为value 1，如果条件为假，则value 2评估为{{1}}。

Answer 2

编辑如果您将使用相同的排序参数两次：

您可以尝试使用Let创建本地参数：

var myofferUnsorted = (from b in MMEntities.OfferDisplays.AsExpandable().Where(pred)
                    **let OrderArg = b.Offers.OfferID**
                   where b.Offers.Accounts.AccountID == accountID && b.Offers.OfferID != 0  && !((from bb in MMEntities.OfferDisplays.AsExpandable().Where(pred)
                         where
                           bb.Offers.Accounts.AccountID == accountID && bb.Offers.OfferID != 0                                  orderby
                         OrderArg descending
                         select new
                         {
                             bb.Offers.OfferID
                         }).Take(10)).Contains(new { b.Offers.OfferID }) &&
                     b.Offers.Accounts.AccountID == accountID 
orderby
                         OrderArg  descending

在这种情况下，您必须将条件嵌入到linq中： let OrderArg = flag ? b.Offers.OfferID : b.Offers.SmthElse

根据Linq的条件更改订单

2 个答案: