实体框架代码首先从0..1级联删除到许多

Question

I'm using this kind of model for a 0..1 to many relationship. A Page must either have a valid book id or null.

public class Book
{
    [Key]
    public Guid Id { get; set; }

    public virtual List<Page> Pages { get; set; }
}

public class Page
{
    [Key]
    public Guid Id { get; set; }

    public virtual Book Book { get; set; }
}

I want to add cascading deletes, so that if a book is deleted then all of its pages are also deleted, not set to null.

I can (only?) do this with the fluent api:

modelBuilder.Entity<Page>()
    .HasOptional(a => a.Book)
    .WithOptionalDependent()
    .WillCascadeOnDelete(true);

Using [Required] is not suitable, because the field is not required.

However, this creates another column Book_Id1 , index and foreign key in the database, rather than adding cascading deletes on the existing FK, because it's defined twice.

If I comment out the Book.Pages property, it works, but I lose the ability to call book.Pages and have to instead call dbcontext.Pages.Where(p => p.Book.Id == book.Id) , which is not ideal because I don't want the calling code to have to know about the dbcontext object.

Is there a way to have both the Book.Pages property and cascading deletes? Perhaps setting both to use the same FK name?

Answer 1

i think in codefirst you have to try this

dbcontext.Page.RemoveRange(book.Pages);
dbcontext.Book.Remove(book);
dbContext.SaveChanges(); 

Answer 2

here what you can do

public class Book
{
    [Key]
    public Guid Id { get; set; }

    public virtual List<Page> Pages { get; set; }
}

public class Page
{
    [Key]
    public Guid Id { get; set; }
    public Guid BookId { get; set;}

    //[ForeignKey("BookId")] you can add the fluent here or during entity builder
    public virtual Book Book { get; set; }
}


modelBuilder.Entity<Page>()
    .HasOptional(a => a.Book)
    .WithMany(a=>a.Pages)
    .HasForeignKey(a=>a.BookId)
    .WillCascadeOnDelete(true);

var pages= dbcontext.Pages.Where(p => p.BookId == book.Id); // this will work

this code should work normally for you