如何在EFCore Select中编写内联If语句(SQL IIF)? [英] How to write Inline If Statement(SQL IIF) in EFCore Select?

问题描述

我有以下Customer表:

Id  First    Last   LocationId
0   John     Doe    2
1   Mary     Smith  4

我的用例需要列级权限(基于实体表中的值).

My use case requires column level permissions(predicated on a value in the Entity's table).

如何通过EFCore进行如下查询?

How can I query like the following thru EFCore?

SELECT Id, First, IIF(LocationId in(2), Last, '') FROM Customer;

仅在LocationId == 2时返回Last.

• 这可以在Linq-to-Entities中作为动态类型完成吗?
• 如果没有，我可以使用FromSql()和 QueryTypes ?
• 我找到了这个如何使用动态选择中的表达式创建内联if语句"以进行空检查.但是我不熟悉Expression类型.但是，这暗示了它的可能性.

• Can this be accomplished in Linq-to-Entities as a dynamic type?
• If not, can I use FromSql() and QueryTypes?
• I found this SO How to create "inline if statement" with expressions in dynamic select for null checking. But I am not familiar with Expression type. This implies its possible however.

推荐答案

我相信您正在寻找使用.Select()方法和三元运算符的方法.像这样:

I believe you're looking to use the .Select() method and ternary operator. So something like this:

context.Customer.Select(c => new { c.Id, c.First, Last = c.LocationId == 2 ? c.Last : "" });

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