实体框架拆分表删除 [英] Entity Framework Split Table Delete

问题描述

我使用EF 4 STE来建模一个Attachment对象。 附件包含名称，说明，日期，最重要的是数据（ byte [] ）。要优化加载，我绝对不需要检索Data属性，直到用户从客户端点击下载为止。

为了遵循这种方法，我使用了描述的表分解技术这里。我将附件表分成附件（名称，说明，日期）和 AttachmentData （数据）。在我的EF模型中，这是一对一的关系。一切都很好，直到我尝试删除附件，而不附加 AttachmentData （即 attachment.AttachmentData == null ）。我得到以下异常：

遇到无效数据。缺少必需的关系。检查StateEntries以确定约束违规的来源。

我看到一个类似的帖子，但我似乎无法使其与STE's和 ApplyChanges 扩展方法。

现在我的数据访问代码很简单：我调用上下文的 ApplyChanges（）后跟 SaveChanges（）。

我已经尝试过一个简单的删除SQL函数并将其映射对实体和实际工作;但是它打破了插入。我似乎无法将所有属性的insert函数映射到两个实体。

有些其他选项的想法可以尝试吗？ Attachment和AttachmentData之间的关系可以是可选的吗？当我使它1到0+时，我得到一个映射错误，说他们的主键可能会碰撞。

打开任何建议。

谢谢！

解决方案

解决方案是类似于链接问题，但您必须使用STE的特定功能 - ApplyChanges ：

  context.Attachments.ApplyChanges（ATT）; 
 if（context.ObjectStateManager.GetObjectStateEntry（att）.State == EntityState.Deleted）
 {
 var data = new AttachmentData（）{Id = att.Id}; 
 context.AttachmentDataSet.Attach（data）; 
 context.AttachmentDataSet.DeleteObject（data）; 
} 
 context.SaveChanges（）; 
  

I'm using EF 4 STE's to model an Attachment object. The Attachment contains a Name, Description, Date, and most importantly Data (byte[]). To optimize loading, I don't want to retrieve the Data property until it's absolutely necessary, i.e. when the user clicks Download from the client.

In an effort to follow this approach, I used the table-splitting technique described here. I split my Attachment table up into Attachment (Name, Description, Date) and AttachmentData (Data). It's a 1-to-1 relationship in my EF model. Everything works great until I try to delete an Attachment without the AttachmentData (i.e. attachment.AttachmentData == null). I get the following exception:

Invalid data encountered. A required relationship is missing. Examine StateEntries to determine the source of the constraint violation.

I saw a similar post, but I can't seem to make it work with STE's and the ApplyChanges extension method.

Right now my data access code is simple: I call context's ApplyChanges() followed by SaveChanges().

I've tried a simple delete SQL function and mapped it to both entities and that actually worked; however it broke the insert. I can't seem to map an insert function for all properties to both entities.

Any ideas on some other options I can try? Can the relationship between Attachment and AttachmentData be optional? When I make it 1 to 0+, I get a mapping error saying that Their primary keys may collide.

Open to any suggestions.

Thanks!

解决方案

The solution is similar to linked question but you must use specific feature of STEs - ApplyChanges:

context.Attachments.ApplyChanges(att);
if (context.ObjectStateManager.GetObjectStateEntry(att).State == EntityState.Deleted)
{
    var data = new AttachmentData() {Id = att.Id};
    context.AttachmentDataSet.Attach(data);
    context.AttachmentDataSet.DeleteObject(data);
}
context.SaveChanges();

这篇关于实体框架拆分表删除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！