什么是“当发生时的情况”？ （T-SQL）使用实体框架？ [英] What is the equivalent of "CASE WHEN THEN" (T-SQL) with Entity Framework?

问题描述

我有一个Transact-SQl请求，我经常使用它，并且我想获得与Entity Framework相同的请求。但是我不知道如何用EF进行 CASE WHEN声明。这是我的请求的简化代码：

I have a Transact-SQl request that I use a lot and I want to get the equivalent with Entity Framework. But I don't know how to make a "CASE WHEN" statement with EF. Here is a simplified code of my request :

SELECT Code,
SUM(CASE WHEN Month=1 THEN Days Else 0 END) AS Jan,
FROM MyTable 
GROUP BY Code

告诉我是否可以使用EF，以及如何使用EF？

Can you tell me if it's possible and how to do this with EF ?

推荐答案

在这种情况下，我会说条件运算符（ p？x：y ）是

In this case, I'd say the conditional operator (p ? x : y) is a good substitute.

// context.MyTable is an IQueryable<MyTable>
var query = from t in context.MyTable
            group t by t.Code into grp
            select
            new {
                Code = grp.Key,
                Jan = grp.Sum(x => x.Month == 1 ? x.Days : 0),
            };

或将 Where 和总和：

                Jan = grp.Where(x => x.Month == 1).Sum(x => x.Days),

我不确定这些SQL确切地解释为什么，但是它们都应具有相同的结果。

I'm not sure what SQL these translate to exactly, but they should both have the same result.

这篇关于什么是“当发生时的情况”？ （T-SQL）使用实体框架？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！