如何设置实体框架以使用可选外键在删除时进行级联？ [英] How do you set Entity Framework to cascade on delete with optional foreign key?

问题描述

我正在尝试将Entity Framework设置为使用可选的外键在删除时进行级联。我先使用代码，我的模型如下所示：

I'm attempting to set Entity Framework to cascade on delete with an optional foreign key. I'm using code first, and my model looks like this:

public class Node
{
    [Key]
    public int ID { get; set; }

    [ForeignKey("Parent")]
    public int? ParentID { get; set; }
    public virtual Node Parent { get; set; }
}

我看到了很多解决方案，它们表明：密钥，但是这对我不起作用，因为父节点可能为空。

I've seen plenty of solutions that suggest, "Just make the foreign key required," but this will not work for me because the parent node may be null.

是否存在不涉及在父节点之前手动删除子节点的解决方案？ ？

Does a solution exist that doesn't involve manually deleting child nodes before parent nodes?

推荐答案

在这里似乎要怪MSSQL。因为我的表是自引用的，所以不可能将delete的级联设置为true。

It looks as though MSSQL is to blame here. Because my table is self-referencing, It is impossible to set cascade on delete to true.

相反，我最后要做的是递归地手动标记每个孩子要删除，然后调用SaveChanges（）并让EntityFramework整理其余部分。

Instead, what I ended up doing was manually marking each child for deletion recursively, then calling SaveChanges() and letting EntityFramework sort out the rest.

这里是一个简单的代码示例，用于说明：

Here is a simple code sample to illustrate:

void Delete(bool recursive = false)
{
    if(recursive)
        RecursiveDelete();

    if(this.Parent != null)
        this.Parent.Children.Remove(this);

    using(var db = new MyContext())
    {
        db.SaveChanges();
    }
}
void RecursiveDelete()
{
    foreach(var child in Children.ToArray())
    {
        child.RecursiveDelete();
        Children.Remove(child);
    }

    using(var db = new MyContext())
    {
        db.Nodes.Attach(this);
        db.Entry(this).State = EntityState.Deleted();
    }
}

这篇关于如何设置实体框架以使用可选外键在删除时进行级联？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！