Question

在模型中列出了类（简化）：

public partial class Category
{
    public Category()
    {
        Topics = new HashSet<Topic>();
    }

    public Guid Id { get; set; }
    public Guid? Category_Id { get; set; }//id for Parent category

    public virtual ICollection<Topic> Topics { get; set; }
}

public partial class Topic
{
    public Topic()
    {
        Posts = new HashSet<Post>();
    }

    public Guid Id { get; set; }
    public string Name { get; set; }
    public Guid Category_Id { get; set; }

    public virtual ICollection<Post> Posts { get; set; }
    public virtual Category Category { get; set; }
}

这里的模型：

public partial class EntityModel : DbContext
{
    public EntityModel()
        : base("name=EntityModelContext")
    {
        Configuration.LazyLoadingEnabled = true;
        Configuration.AutoDetectChangesEnabled = true;
        Debug.WriteLine("Context Created");
    }

    public virtual DbSet<Category> Category { get; set; }
    public virtual DbSet<Post> Post { get; set; }
    public virtual DbSet<Topic> Topic { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Category>()
            .HasMany(e => e.Topics)
            .WithRequired(e => e.Category)
            .HasForeignKey(e => e.Category_Id)
            .WillCascadeOnDelete(true);

        modelBuilder.Entity<Topic>()
            .HasMany(e => e.Posts)
            .WithRequired(e => e.Topic)
            .HasForeignKey(e => e.Topic_Id)
            .WillCascadeOnDelete(true);
    }
}

问题：当我试图删除子类别（具有NOT NULL Category_Id）=＆gt;删除成功，但是当我需要删除根类别（Category_Id = NULL）时，有一个例外：DELETE语句与REFERENCE约束“FK_Topic_Category”冲突。是的，我可以先删除根类别中的参考主题，然后删除类别。但是想知道为什么在root情况下级联删除不起作用。

Answer 1

好的，只需在数据库注释中将ON DELETE CASCADE添加到子实体的FK中。

使用EntityFramework删除级联

1 个答案: