在EF中的ObjectMaterialize不是在第一级查询上触发 [英] ObjectMaterialize in EF not firing on first level query

问题描述

我有一个查询，如：

 查询语法1  - 不触发某个处理程序; 
 var results =（从我在db.mytable 
中选择新的myObject（）{
 column1 = i.Prop1 
}）ToList（）; 
 
查询语法2  - 触发somehandler事件; 
 var results =（从我在db.mytable 
中选择I）.toList（）;我的ContextClass中有
  

 （（IOjectContextAdapter）this）.ObjectContext.ObjectMaterialized + = somehandler; 
  

我看到的唯一区别是第一个查询从选择结果构建一个新对象。 p>

任何意图为什么事件不会触发？

解决方案

事件仅为实体对象投影而触发，这就是为什么您看到这种行为。

如果查询使用投影并且没有匹配的实体，结果将实现为DbDataRecords（或使用LINQ to Entities查询时的匿名类型）而不是实体对象，参考编程实体框架（Julia Lerman）P-244）

ObjectMarialized状态的定义

当新的

参考资料。 https：// msdn.microsoft.com/en-us/library/system.data.objects.objectcontext.objectmaterialized(v=vs.110).aspx

自投影不会创建Entity对象，它不会触发事件。

I have a query such as:

Query Syntax 1 - Does not fire the somehandler;
var results = (from I in db.mytable
              select new myObject() {
                        column1 = i.Prop1
              }).ToList();

Query Syntax 2 - Does fires the somehandler event;
var results = (from I in db.mytable
               select I).toList();

in my ContextClass I have something like this:

((IOjectContextAdapter)this).ObjectContext.ObjectMaterialized +=  somehandler;

The only difference I see is that the first query builds a new object from the select results.

Any idea why the event wouldn't fire?

解决方案

The event fires only for Entity object projections, that is why you see this behaviour.

"If the query used a projection and there is no matching entity, the results are materialized into DbDataRecords (or anonymous types when a LINQ to Entities query was used) instead of entity objects," Ref -Programming Entity Framework (Julia Lerman)P-244)

The definition for ObjectMarialized states

Occurs when a new entity object is created from data in the data source as part of a query or load operation.

Ref. https://msdn.microsoft.com/en-us/library/system.data.objects.objectcontext.objectmaterialized(v=vs.110).aspx

Since the projection does not create an Entity object, it does not fire the event.

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