为什么Entity Framework查询不返回未保存的实体 [英] Why do Entity Framework queries not return unsaved entities

问题描述

考虑以下代码：

var Products_First = (from Entities.Product p in myContext.Product  
                      select p);

Entities.Product newProduct = new Entities.Product();
newProduct.Name = "New Product";
myContext.Products.AddObject(newProduct);

var Products_Again = (from Entities.Product p in myContext.Product  
                      select p);

请注意， Products_Again 被查询而不保存

Notice here that Products_Again is queried without saving the context, that is myContext.SaveChanges() is not called.

Products_Again 包含与 Products_First 相同数量的产品。为什么是这样？新的产品由相同的上下文对象添加和跟踪。为什么我不能在新的查询结果中看到新产品？

Products_Again contains the same number of products as Products_First. Why is this? A new Product is added and tracked by the same context object. Why can not I see the new product in the new query results?

在上下文中添加新对象后，是否有一种方法来达到新对象而不保存更改？ / p>

After adding new object to the context is there a way to reach the new object without saving changes?

推荐答案

类型 ObjectQuery< T> 的属性，如 myContext.Product ，始终查询数据库。这就是他们所做的。

Properties of type ObjectQuery<T>, like myContext.Product, always query the DB. That's what they do.

在EF 4.1中，您可以使用 DbSet< T> .Local 来查询内存。

In EF 4.1 you can use DbSet<T>.Local to query memory.

在EF< 4.1你将使用：

In EF < 4.1 you would use:

ObjectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Added).Select(o => o.Entity).OfType<Product>()

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