使用EF Code First Approach时，MVC .Net Cascade删除 [英] MVC .Net Cascade Deleting when using EF Code First Approach

问题描述

我很新的MVC，我有级联删除的麻烦。对于我的模型，我有以下2个类：

  public class Blog 
 {
 [Key] 
 public int Id {get;组; 
 [必需] 
 public string Name {get;组; } 
 [DisplayFormat（）] 
 public virtual ICollection< BlogEntry> BlogEntries {get;组; } 
 public DateTime CreationDateTime {get;组; } 
 public string UserName {get;组; 
} 
 
 public class BlogEntry 
 {
 [Key] 
 public int Id {get;组; } 
 [必需] 
 public string标题{get;组; } 
 [必需] 
 public string Summary {get;组; } 
 [必需] 
 public string Body {get;组; } 
 public List< Comment>评论{get;组; } 
 public List< Tag>标签{get;组; } 
 public DateTime CreationDateTime {get;组; } 
 public DateTime UpdateDateTime {get;组; } 
 public virtual Blog ParentBlog {get;组; } 
 
} 
  

对于我的控制器，我设置他在删除帖子后面返回：

  [HttpPost，ActionName（Delete）] 
 public ActionResult DeleteConfirmed（int id）
 {
 Blag blog = db.Blogs.Find（id）; 
 
 foreach（var blogentry in blog.BlogEntries）
 {
 // blogentry = db.BlogEntries.Find（id）; 
 db.BlogEntries.Remove（blogentry）; 
} 
 db.Blogs.Remove（blog）; 
 db.SaveChanges（）; 
 return RedirectToAction（Index）; 
} 
  

问题是它不工作，无论什么; 我阅读这个帖子，但我似乎只适用于关系是一对一的模型，所以我迷失在这里，我有搜索无处不在，找不到这个问题的解决方案，如果有人可以指出我错过了，真的很好:)，谢谢提前，再次，原谅我的nooobness我刚刚开始，但想要解决一个大项目，以便能够学到很多。

解决方案

这是因为EF默认情况下不强制执行级联删除用于可选关系。您的模型中的关系被推断为可选的。

您可以添加一个不可为空的标量属性（ BlogId ） FK

  public class BlogEntry 
 {
 [Key] 
 public int Id {get ;组; } 
 [必需] 
 public string标题{get;组; } 
 [必需] 
 public string Summary {get;组; } 
 [必需] 
 public string Body {get;组; } 
 public List< Comment>评论{get;组; } 
 public List< Tag>标签{get;组; } 
 public DateTime CreationDateTime {get;组; } 
 public DateTime UpdateDateTime {get;组; } 
 
 public int ParentBlogId {get;组; } 
 
 public virtual Blog ParentBlog {get;组; } 
} 
  

或使用流畅的API配置此API

  modelBuilder.Entity< BlogEntry>（）
 .HasRequired（b => b.ParentBlog）
 .WithMany（b => b .BlogEntries）
 .WillCascadeOnDelete（true）; 
  

I'm pretty new to MVC and i'm having troubles with cascade deleting. For my model I the following 2 classes:

    public class Blog
    {
        [Key]
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }
        [DisplayFormat()]
        public virtual ICollection<BlogEntry> BlogEntries { get; set; }
        public DateTime CreationDateTime { get; set; }
        public string UserName { get; set; }
    }

    public class BlogEntry
    {
        [Key]
        public int Id { get; set; }
        [Required]
        public string Title { get; set; }
        [Required]
        public string Summary { get; set; }
        [Required]
        public string Body { get; set; }
        public List<Comment> Comments { get; set; }
        public List<Tag> Tags { get; set; }
        public DateTime CreationDateTime { get; set; }
        public DateTime UpdateDateTime { get; set; }
        public virtual Blog ParentBlog { get; set; }

    }

And for my controller I set he following on delete post back:

[HttpPost, ActionName("Delete")]
public ActionResult DeleteConfirmed(int id)
{
    Blag blog = db.Blogs.Find(id);

    foreach (var blogentry in blog.BlogEntries)
    {
        //blogentry = db.BlogEntries.Find(id);
        db.BlogEntries.Remove(blogentry);
    }
    db.Blogs.Remove(blog);
    db.SaveChanges();
    return RedirectToAction("Index");
}

Problem is it wont work no matter what; I read this post but i seem to only work for models where the relation is one to one, so i'm lost here, i have search everywhere, and can't find the solution for this problem, if some could point out what i'm missing it would be really nice :), thanks in advance, and again, pardon my nooobness i'm just getting started, but wanted to tackle a big project to be able to learn a lot.

解决方案

That is because EF by default does not enforce cascade deletes for optional relationships. The relationship in your model is inferred as optional.

You can add a non nullable scalar property(BlogId) of the FK

public class BlogEntry
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string Title { get; set; }
    [Required]
    public string Summary { get; set; }
    [Required]
    public string Body { get; set; }
    public List<Comment> Comments { get; set; }
    public List<Tag> Tags { get; set; }
    public DateTime CreationDateTime { get; set; }
    public DateTime UpdateDateTime { get; set; }

    public int ParentBlogId { get; set; }

    public virtual Blog ParentBlog { get; set; }
}

Or configure this using fluent API

   modelBuilder.Entity<BlogEntry>()
            .HasRequired(b => b.ParentBlog)
            .WithMany(b => b.BlogEntries)
            .WillCascadeOnDelete(true);

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