EF多对多级联删除

问题描述

我有一个问题.我有一些看起来像这样的班级:

I have an issue.I have some classes that look like this:

public class Question
{
    public int Id { get; set; }
    [Required] [MaxLength(255)] public string Text { get; set; }
    public int CriteriaId { get; set; }
    public int QuestionGroupId { get; set; }

    public QuestionGroup QuestionGroup { get; set; }
    public virtual IList<Answer> Answers { get; set; }
    public virtual Criteria Criteria { get; set; }
}

public class Answer
{
    public int Id { get; set; }
    [Required] [MaxLength(255)] public string Text { get; set; }
    public int QuestionId { get; set; }

    public Question Question { get; set; }
    public virtual IList<State> States { get; set; }
}

public class Criteria
{
    public int Id { get; set; }
    [Required] [MaxLength(100)] public string Name { get; set; }

    public virtual IList<State> States { get; set; }
    public IList<Question> Questions { get; set; }
}

public class State
{
    public int Id { get; set; }
    public int CriteriaId { get; set; }
    [Required] [MaxLength(100)] public string Name { get; set; }
    public int Score { get; set; }

    public virtual IList<Filter> Filters { get; set; }
    public Criteria Criteria { get; set; }
}

它们之间存在多对多关系，因此我创建了此映射:

They have a many to many relationship, so I created this mapping:

modelBuilder.Entity<Answer>()
    .HasMany(m => m.States)
    .WithMany()
    .Map(m => {
        m.MapLeftKey("AnswerId");
        m.MapRightKey("StateId");
        m.ToTable("AnswerStates");
    });

当我尝试更新数据库时，出现有关外键的错误.因此，我添加了这一行(作为临时解决方法):

When I tried to update my database I get an error about foreign keys.So I added this line (as a temporary fix):

modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();

但是我需要级联删除.我似乎无法弄清楚为什么它不让我拥有它.尝试包括级联删除时出现的错误是:

But I need the cascading delete.I can't seem to figure out why it won't let me have it.The error I get when trying to include cascading deletes is:

我希望我提供了足够的信息.有谁知道我可以做些什么来允许级联删除(我需要能够删除 State 或 Answer ，然后从 AnswerStates中删除记录

I hope I have provided enough information. Does anyone know what I can do to allow the cascading delete (I need to be able to delete a State or an Answer and it to remove the record from AnswerStates

推荐答案

这与另一个问题()我今天在回答.只是您的情况要复杂一些.

This is pretty much the same as another question (Deleting only one entry from Many-to-Many relationship) I was answering today. Just your case is a bit more complicated.

您的情况下，多级联路径是从 Criteria 到 AnswerStates .删除 Criteria 记录时， Criteria-> States-> AnswerStates 或 Criteria->问题->答案->答案状态关系.

The multiple cascade path in your case is from Criteria to AnswerStates. When deleting a Criteria record, the AnswerStates records can be deleted either by Criteria->States->AnswerStates or Criteria->Questions->Answers->AnswerStates relationships.

解决方案始终是相同的-关闭关系 cascade delete 之一，然后手动或通过触发器处理删除.

The solution is always one and the same - turn one of the relationships cascade delete off and handle deletion either manually or via trigger.

在这种情况下，我的建议是关闭 Criteria-> States 级联删除:

In this particular case, my suggestion is to turn Criteria->States cascade delete off:

modelBuilder.Entity<Criteria>()
    .HasMany(m => m.States)
    .WithRequired(d => d.Criteria)
    .HasForeignKey(d => d.CriteriaId)
    .WillCascadeOnDelete(false);

并在删除条件之前使用类似的内容:

and use something like this before deleting a Criteria:

db.States.RemoveRange(db.States.Where(s => s.CriteriaId == criteriaId_to_be_removed));

这篇关于EF多对多级联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！