LINQ排序依据FK使用左连接 [英] LINQ orderby FK using a left join

问题描述

我有以下的code：

from _categories in context.SCT_Categories
join _categoryOrders in context.SCT_CategoryOrders
on _categories.ID equals _categoryOrders.CategoryID into joinedData
from _categoryOrders in joinedData.DefaultIfEmpty()
orderby _categoryOrders.OrderIndex descending 
select _categories

这不左连接类别和categoryOrders

Which does a left join on categories and categoryOrders

对于每一个catgoryOrder还有一类。

For every catgoryOrder there is a category.

这工作得很好，只是当我想通过OrderIndex订购（可以为null，999），它把所有空的查询顶部（即空返回的关系，其中一类没有categoryOrder）。

This works well, except that when I want to order by OrderIndex (Can be null to 999) it places all empty (i.e. null returned relationships where a category has no categoryOrder) at the top of the query.

我要如何改变这种把空值在列表的末尾？ pfereably $ P $无查询后迭代改变空值999。

How do I change this to put empty values at the end of the list? Prefereably without an iteration after the query to change empty values to 999.

谢谢

JD

推荐答案

我没有尝试这样做（的IQueryProvider可能不喜欢它）

I haven't tried this (the IQueryProvider might not like it)

let orderIndex = _categoryOrders.OrderIndex ?? int.MaxValue

就在您的排序依据，并在orderIndex订单前代替。

Right before your orderby, and order on orderIndex instead.

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