.net 我可以使用数据注释通过 Entity Framework 4.1 RC 执行级联删除吗？
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Can I use Data Annotations to perform a Cascade Delete with Entity Framework 4.1 RC?
提问by Bender
When using data annotations with EF4.1 RC is there an annotation to cause cascade deletes?
在 EF4.1 RC 中使用数据注释时，是否有导致级联删除的注释？
public class Category
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
public ICollection<Product> Products { get; set; }
}
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public Category Category { get; set; }
}
Using this model the constraint generated is:
使用此模型生成的约束为：
ALTER TABLE [Product] ADD CONSTRAINT [Product_Category]
FOREIGN KEY ([Category_Id]) REFERENCES [Categorys]([Id])
ON DELETE NO ACTION ON UPDATE NO ACTION;
If not how is it achieved?
如果不是，它是如何实现的？
回答by Bender
Putting required on the Product table Category relationship field solves this
在 Product 表 Category 关系字段上放置 required 解决了这个问题
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
[Required] //<======= Forces Cascade delete
public Category Category { get; set; }
}
回答by Tyson
I like to turn off cascade delete by default (by removing the OneToManyCascadeDeleteConvention)
我喜欢默认关闭级联删除（通过删除OneToManyCascadeDeleteConvention）
I was then hoping to add them back in via annotations, but was surprised that EF doesn't include a CascadeDeleteAttribute.
然后我希望通过注释将它们添加回来，但很惊讶 EF 不包含CascadeDeleteAttribute.
After spending way too long working around EF's ridiculous internal accessor levels, the code in this gist adds a convention that allows attributes to be used: https://gist.github.com/tystol/20b07bd4e0043d43faff
在解决 EF 荒谬的内部访问器级别上花费了太长时间后，此要点中的代码添加了一个允许使用属性的约定：https: //gist.github.com/tystol/20b07bd4e0043d43faff
To use, just stick the [CascadeDelete]on either end of the navigation properties for the relationship, and add the convention in your DbContext's OnModeCreating callback. eg:
要使用，只需[CascadeDelete]在关系的导航属性的两端粘贴，并在 DbContext 的 OnModeCreating 回调中添加约定。例如：
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Add<CascadeDeleteAttributeConvention>();
}
And in your model:
在你的模型中：
public class BlogPost
{
public int Id { get; set; }
public string Title { get; set; }
public string Content { get; set; }
[CascadeDelete]
public List<BlogPostComment> Comments { get; set; }
}
回答by taylonr
Not sure on Data Annotations, but you can add it in the database by modifying the actual relationship.
不确定数据注释，但您可以通过修改实际关系将其添加到数据库中。
Looks like the answer is no for data annotations: http://social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/394821ae-ab28-4b3f-b554-184a6d1ba72d/
看起来数据注释的答案是否定的：http: //social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/394821ae-ab28-4b3f-b554-184a6d1ba72d/
This question appears to show how to do it with the fluent syntax, but not sure if that applies for 4.1 RC EF 4.1 RC: Weird Cascade Delete
这个问题似乎展示了如何使用流畅的语法来做到这一点，但不确定这是否适用于 4.1 RC EF 4.1 RC: Weird Cascade Delete
回答by j00hi
As an additional example to Tyson's answer, I use the [CascadeDelete]attribute like follows in an entity, which successfully adds the "Cascade" delete rule to the Parent-Childrelation.
作为Tyson's answer的附加示例，我[CascadeDelete]在实体中使用如下属性，该属性成功地将“级联”删除规则添加到Parent-Child关系。
public class Child
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
[SkipTracking]
public Guid Id { get; set; }
[CascadeDelete]
public virtual Parent Parent { get; set; }
[Required]
[ForeignKey("Parent")]
public Guid ParentId { get; set; }
}
