EF 5 - 获取导航属性的外键值 [英] EF 5 - Get foreign key value for navigation property

问题描述

我想获取导航属性的外键值，而无需定义外键属性（在导入属性加载之前）。

为什么？

我们缓存（例如）所有状态 - 对象应用程序范围（是的，我们不能使用枚举）。当我们将具有导航属性的对象加载到此状态类时，存储库将将该属性设置为缓存项。

我可以使用外键属性，但是因为EF知道密钥，我想从EF获取它（可能通过RelationshipManager或导航属性的DBEntityReference），但我似乎找不到。

<注意：我正在使用EF5，代码首先在.Net 4.5中

解决方案

answer（on stackoverflow）from Slauma （不知道我是否应该将其标记为重复？）。我不得不改变代码来处理一个具有多重关系的实体。很多东西还是很丑，但是它的作用是：）

  RelationshipManager relMgr =（（IObjectContextAdapter）context）.ObjectContext.ObjectStateManager。 GetRelationshipManager（文件）; 
 IEnumerable< IRelatedEnd> relEnds = relMgr.GetAllRelatedEnds（）; 
 IRelatedEnd relEnd = relEnds.Where（r => r.RelationshipName.EndsWith（Document_Status））。Single（）; 
 EntityReference< Status> entityRef = relEnd作为EntityReference< Status> ;;; 
 var entityKey = entityRef.EntityKey; 
 
 short statusId =（short）entityKey.EntityKeyValues [0] .Value; 
  

唯一的缺点是（据我所知，希望有人找到更好的方式）一旦您分离实体或使用AsNoTracking（）加载它时，此信息就会丢失。

I want to get the foreign key value for a navigation property, without having to define the foreign key property (before the navigation property is loaded).

Why?

We cache (for instance) all "status"-objects application wide (yes we couldn't use enums for this). When we load an object with a navigation property to this status-class the repository will set the property to the cached item.

I could go with a foreign key property, but since EF knows the key, I would like to get it from EF (maybe through the RelationshipManager or the DBEntityReference for the navigation property) but I can't seem to find it.

Note: I am using EF5, code first in .Net 4.5

解决方案

I found an answer (on stackoverflow) from Slauma (not sure if I should mark this as duplicate?). I had to change the code a litle to handle an entity with multiple relations. A lot of stuff is still ugly but it works :)

RelationshipManager relMgr = ((IObjectContextAdapter)context).ObjectContext.ObjectStateManager.GetRelationshipManager(document);
IEnumerable<IRelatedEnd> relEnds = relMgr.GetAllRelatedEnds();
IRelatedEnd relEnd = relEnds.Where(r => r.RelationshipName.EndsWith("Document_Status")).Single();
EntityReference<Status> entityRef = relEnd as EntityReference<Status>;
var entityKey = entityRef.EntityKey;

short statusId =(short)entityKey.EntityKeyValues[0].Value;

The only downside is that (As far as I can tell. Hope someone finds a better way?) this information is lost as soon as you detach the entity or when you load it with AsNoTracking().

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