Linq :查询联接和等于(变量)不起作用
Linq :查询联接和等于(变量)不起作用
提问于 2018-06-01 03:16:55
Dim ID_Section as Int32 = 10
Dim Query = From Book1 In db.Book1
Group Join Section In db.Section On CInt(Book1.ID_Section) Equals Section.ID_section _
And Section.ID_section Equals (ID_Section) Into Section_join = Group
From Section In Section_join.DefaultIfEmpty()
Select
Book1.ID_Book,
Book1.Name_Book,
ID_section = Section.ID_section,
Name_Section = Section.Name_Section错误出现在变量id_Section中，因为Linq不接受来自外部的值，这在我看来是当然的。
这里有错误：
And Section.ID_section Equals (ID_Section) 在SQL查询中使用位置：
Declare @ID_Section int
SELECT Book.ID_Book, Book.Name_Book, Section.ID_section, Section.Name_Section
FROM Book LEFT OUTER JOIN
Section ON Book.ID_Section = Section.ID_section and Section.ID_section = @ID_Section
where Book.ID_Book =1回答 1
Stack Overflow用户
回答已采纳
发布于 2018-06-01 05:19:48
在带有lambda语法的db.Section上使用Where：
Dim Query = From Book1 In db.Book1
Group Join Section In db.Section.Where(Function(s) s.ID_section = ID_Section)
On CInt(Book1.ID_Section) Equals Section.ID_section _
Into Section_join = Group
From Section In Section_join.DefaultIfEmpty()
Select
Book1.ID_Book,
Book1.Name_Book,
ID_section = Section.ID_section,
Name_Section = Section.Name_Section或者，您可以将Where应用于Join结果：
Dim Query = From Book1 In db.Book1
Group Join Section In db.Section
On CInt(Book1.ID_Section) Equals Section.ID_section _
Into Section_join = Group
From Section In Section_join.Where(Function(s) s.ID_section = ID_Section).DefaultIfEmpty()
Select
Book1.ID_Book,
Book1.Name_Book,
ID_section = Section.ID_section,
Name_Section = Section.Name_Section页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/50631322
复制相关文章
相似问题