处理join中的EF 4 C#.Face问题。sql语法
Select a.Code, b.Name from DepartmentMaster a
Join DepartmentDetail b on isnull( a.ID,0) =isnull( b.ID,0)
注意: a.ID和b.ID都可以为空
想要上面的语法输出放入Linq语法.Bellow语法对我不起作用
Var r=from a in DepartmentMaster
Join b in DepartmentDetail on a.ID equals b.ID
Select a.Code,b.Name
需要帮助来编写sql语法isnull()在linq ef中可比的过程。
如果有任何疑问,请提出来。
发布于 2013-08-26 23:10:32
如果id为null,您可以使用null-coalescing运算符提供默认值:
from c in DepartmentMaster
join b in DepartmentDetail
on (a.ID ?? 0) equals (b.ID ?? 0)
select new {
a.Code, b.Name
}
将生成查询的
SELECT [t0].[Code], [t1].[Name] AS [ID1]
FROM [DepartmentMaster] AS [t0]
INNER JOIN [DepartmentDetail] AS [t1]
ON (COALESCE([t0].[ID],@p0)) = (COALESCE([t1].[ID],@p1))
这与ISNULL
不完全相同,但结果应该是相同的。
发布于 2013-08-26 23:08:12
这可能会对你有帮助
Var r=from a in DepartmentMaster
Join b in DepartmentDetail on a.(x => (int?)a.ID) ?? 0 equals b.(y => (int?)b.ID) ?? 0
Select a.Code,b.Name
发布于 2013-08-26 23:14:21
你可以使用DefaultIfEmpty
,它用一个缺省值的集合替换一个空集合。因为int的默认值是0
var r=from a in DepartmentMaster
join b in DepartmentDetail on a.ID.DefaultIfEmpty() equals b.ID.DefaultIfEmpty()
Select a.Code,b.Name
https://stackoverflow.com/questions/18447156
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