实体框架 - 预先加载相关实体 [英] Entity Framework - Eager loading related entities
问题描述
我使用实体框架4 MVC和需要确保任何引用的实体我想在我看来，使用控制器方法返回之前已加载，否则认为吐出来的是可怕的：
I'm using Entity Framework 4 with MVC and need to ensure any referenced entities I want to use in my view have been loaded before the controller method returns, otherwise the view spits out the dreaded:
的ObjectContext的实例已被释放，并可以不再被用于需要连接的操作。
The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.
在从上下文中选择直，我就可以使用包含（字符串）要包括在生成的SQL查询方法，迫使他们：
When selecting straight from the context, I can just use the Include(string) method to force them to be included in the generated SQL query:
var sellers = context.Sellers.Include("Recommendations.User").ToList();
不过，如果我有（例如）接受一个实体，需要加载的所有项目一个辅助方法，也没有包含方法可用。
void Test(Seller seller)
{
// ensure all recommendations and their users are loaded
}
的蛮力的方法是遍历他们：
The brute force approach is to loop through them:
foreach (var recommendation in seller.Recommendations)
recommendation.User.ToString(); // just force a load
如果我有100个建议，这将创造背后的幕后101 SQL查询。理想的情况是我想的方法/方法，加载所有建议和用户只有单趟SQL对象。
If I have 100 recommendations, this will create 101 SQL queries behind-the-scenes. Ideally I want a method/approach that loads all Recommendation AND User objects with only a single trip to SQL.
给我钱。
修改我不是在讨论这是否是一个好的或坏的建筑很感兴趣。我已经简化我的方案为客户着想的问题。你可以做什么，我要问的EF API？
EDIT I'm not really interested in discussing whether this is a good or bad architecture. I've simplified my scenario for the sake of the question. Can you do what I'm asking with the EF API?
编辑2
<一个href="http://stackoverflow.com/questions/3671193/entity-framework-eager-loading-related-entities/3671354#3671354">Ladislav's编辑提供了一种新的方法的希望，但似乎我不太有。
Ladislav's edit offered hope of a new approach, but it seems I'm not quite there.
我可以实现我通过这样想：
I can achieve what I want via this:
context.Sellers.Include("Recommendations.User").Single(s => s.Id == seller.Id);
这个方法不会使用正常工作 LoadProperty ...
This approach doesn't work using LoadProperty...
context.LoadProperty(seller, "Recommendations.User");
......，因为它失败，出现错误...
...as it fails with the error...
指定的导航属性Recommendations.User找不到。
The specified navigation property Recommendations.User could not be found.
如果你没有提及的上下文无论这些方法的工作
Neither of these approaches work if you don't have a reference to the context.
推荐答案
这是一个老问题，但在EF6可以完成像的这个：
This is an old question, but in EF6 you can accomplish loading dependent objects on an entity like this:
context.Entry(seller).Collection(s => s.Recommendations).Query().Include(r => r.User)).Load();
这将加载所有建议及相关用户对于给定的卖家
That would load all Recommendations and their related Users for the given seller
这篇关于实体框架 - 预先加载相关实体的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
