将左外连接查询转换为实体框架查询

发布于 2024-11-04 17:42:14 字数 196 浏览 0 评论 0原文

我有一个 sql 语句，我希望能够将其转换为 EF4。

它是一个简单的左外连接，看起来

SELECT * 
FROM EntryDate 
LEFT OUTER JOIN Member on Member.CardId = EntryDate.CardID

如何使用实体框架 4 来执行此操作？

原文

I have a sql statement that I want to be able to convert into EF4.

Its a simple Left outer join that looks like

SELECT * 
FROM EntryDate 
LEFT OUTER JOIN Member on Member.CardId = EntryDate.CardID

how do I do this using the entity framework 4?

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梦里梦着梦中梦 2024-11-11 17:42:14

如果您的模型中有映射的关系，您可以简单地使用导航属性，因为它们总是使用左连接：

var data = members.EntryDates;

我希望您没有这样的关系，因为 CardId 看起来不像 的主键会员 或EntryDate。

如果您没有导航属性，则必须使用

var query = from m in context.Members
            join e in context.EntryDates on m.CardId equals e.CardId into x
            from res in x.DefaultIfEmpty()
            select new
            {
               Member = m,
               EntryDate = res
            };

这仅适用于 EFv4+，因为 EFv1 不支持 DefaultIfEmpty。

If there is relation mapped in your model you can simply use navigation properties because they always use left join:

var data = members.EntryDates;

I expect you don't have such relation because CardId doesn't look like primary key of Member or EntryDate.

If you don't have navigation properties you must use

var query = from m in context.Members
            join e in context.EntryDates on m.CardId equals e.CardId into x
            from res in x.DefaultIfEmpty()
            select new
            {
               Member = m,
               EntryDate = res
            };

This works only in EFv4+ because EFv1 didn't support DefaultIfEmpty.

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