实体框架4：访问部分实体类中的当前数据文本 [英] Entity Framework 4: Access current datacontext in partial entity class

问题描述

我想使用方法和属性在部分类中扩展一个EF实体。我经常这样做。
但现在我需要将来自该实体的数据与其他实体的数据进行组合。因此，我需要能够访问实体objectcontext（如果附加）来进行这些查询。
有没有办法从其中获取实体objectcontext？

Thanx！

解决方案

即使不推荐，我自己不使用它（如Ladislav所说：坏的设计），我偶然发现一个解决方案：

http://blogs.msdn.com/b/alexj/archive/2009/06/08/tip-24-how-to-get-the-objectcontext-from-an-entity .aspx

扩展方法：

  public static ObjectContext GetContext（
 this IEntityWithRelationships entity 
）
 {
 if（entity == null）
 throw new ArgumentNullException（entity）; 
 
 var relationshipManager = entity.RelationshipManager; 
 
 var relatedEnd = relationshipManager.GetAllRelatedEnds（）
 .FirstOrDefault（）; 
 
 if（relevantEnd == null）
抛出新异常（找不到关系）; 
 
 var query = relatedEnd.CreateSourceQuery（）as ObjectQuery; 
 
 if（query == null）
 throw new Exception（实体被分离）; 
 
 return query.Context; 
}  

在实体中

  var myContext = this.GetContext（）as MyEntities;  

I want to extend an EF entity in a partial class with methods and properties. I've done this quite often. But now I would need to combine data from this entity with data from other entities. I would therefore need to able to access the entities objectcontext (if attached) to make these queries. Is there a way to get the entities objectcontext from within it?

Thanx!

解决方案

Even though it is not recommended, and I myself don't use it (as Ladislav stated: bad design), I stumbled upon a solution:

http://blogs.msdn.com/b/alexj/archive/2009/06/08/tip-24-how-to-get-the-objectcontext-from-an-entity.aspx

Extension Method:

public static ObjectContext GetContext( 
   this IEntityWithRelationships entity 
) 
{ 
    if (entity == null)  
       throw new ArgumentNullException("entity"); 

    var relationshipManager = entity.RelationshipManager; 

    var relatedEnd = relationshipManager.GetAllRelatedEnds() 
                                        .FirstOrDefault(); 

    if (relatedEnd == null)  
       throw new Exception("No relationships found"); 

    var query = relatedEnd.CreateSourceQuery() as ObjectQuery; 

    if (query == null)  
       throw new Exception("The Entity is Detached"); 

    return query.Context; 
}

within the entity

var myContext = this.GetContext() as MyEntities;

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