当我尝试使用“Include(”PropertyName“)”“时,为什么会得到”Argument“异常在查询EF? [英] Why do I get Argument exception when I try to use "Include("PropertyName")" in query EF?
问题描述
我有以下代码
var query = BAL.ApplicationInfo.db.Items.Include("Units").ToList();
但它给我这个错误
值不能为空。参数名称:来源
Value cannot be null. Parameter name: source
我的项目实体有一个名为Units的属性,实际上在项之间有关系
和单位
实体。但是我想加载父记录的子记录,但是当我尝试使用上面的代码查询时,我收到上述错误。
My Item entity has a property called "Units" , actually there is relation between Items
and Units
entities. However I want to load child records with parent records, but I am getting the above error whenever I try to query with above code.
有人可以帮助我完成这项工作吗?
Can someone help me to get this done ?
我的上下文是一个DBcontext而不是ObjectContext
My Context is a DBcontext not a ObjectContext
推荐答案
问题。其实问题是我没有一个使用
指令到$ code> System.Data.Entity 命名空间在我的顶部类。
I solved the problem. Actually the problem was I didn't have a using
directive to System.Data.Entity
namespace at the top of my class.
甚至以为我可以在我的查询中使用Include(PropertyName)
名称,我无法使用Include(x => x.Childs)
。但是使用System.Data.Entity添加在我的课堂之上,我可以使用
Include
在这两种方式查询,我的错误解决了。
Even thought I could use "Include("PropertyName)"
name in my query, I couldn't use "Include(x=> x.Childs)"
. But after adding "using System.Data.Entity"
on top of my class I can use "Include"
in these both ways on a query and my error is solved.
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