为什么实体框架需要一个ICollection来进行延迟加载？ [英] Why does the entity framework need an ICollection for lazy loading?

问题描述

我想写一个丰富的域类，如

I want to write a rich domain class such as

public class Product    
{    
   public IEnumerable<Photo> Photos {get; private set;}    
   public void AddPhoto(){...}    
   public void RemovePhoto(){...}
 }

但实体框架（V4代码第一种方法）需要一个ICollection类型进行延迟加载！上述代码不再像设计一样工作，因为客户端可以绕过AddPhoto / RemovePhoto方法，直接调用ICollection上的add方法。这不是很好。

But the entity framework (V4 code first approach) requires an ICollection type for lazy loading! The above code no longer works as designed since clients can bypass the AddPhoto / RemovePhoto method and directly call the add method on ICollection. This is not good.

public class Product    
{    
   public ICollection<Photo> Photos {get; private set;} //Bad    
   public void AddPhoto(){...}    
   public void RemovePhoto(){...}    
 }

尝试使用EF4实现DDD变得非常令人沮丧。为什么选择ICollection进行延迟加载？

It's getting really frustrating trying to implement DDD with the EF4. Why did they choose the ICollection for lazy loading?

我如何克服这个问题？ NHibernate为我提供了更好的DDD体验吗？

How can i overcome this? Does NHibernate offer me a better DDD experience?

推荐答案

我想我找到了解决方案...更多详情请看这里： a href =http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/47296641-0426-49c2-b048-bf890c6d6af2/ =noreferrer> http：//social.msdn .microsoft.com /论坛/ en-US / adodotnetentityframework / thread / 47296641-0426-49c2-b048-bf890c6d6af2 /

I think i found the solution...See here for more details: http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/47296641-0426-49c2-b048-bf890c6d6af2/

本质上你想让ICollection类型受保护，并将其用作公共IEnumerable的支持集合

Essentially you want to make the ICollection type protected and use this as the backing collection for the public IEnumerable

public class Product
{

   // This is a mapped property
   protected virtual ICollection<Photo> _photos { get; set; }

   // This is an un-mapped property that just wraps _photos
   public IEnumerable<Photo> Photos
   {
      get  { return _photos; }
   }

   public void AddPhoto(){...}
   public void RemovePhoto(){...}

} 

为了延迟加载工作，类型必须实现ICollection，访问必须是公共的或受保护的。

For lazy loading to work the type must implement ICollection and the access must be public or protected.

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