aspnetzero prevent soft delete if row is referenced in another table

Question

I am Using ASPNETZero in my Application Where the Entities are Soft Deleted with the help of the below Code Snippet.

var query = Repository.GetAll()
            .Where("Id == @0", input.Id)
            .ProjectTo<TDto>(ItemMapper);
        var dto = await AsyncExecuter.SingleAsync(query, true);
        await base.DeleteAsync(input);
        await CurrentUnitOfWork.SaveChangesAsync();
        await EventBus.TriggerAsync(new DestroyEvent<TDto>(dto));

It sets the IsDeleted Property to False but I want to check Whether the Value Exist in the Reference Table, If Exist then don't Delete (Soft Delete) the Entity

Answer 1

If you created Entites with code-first like this:

public class Book
{ 
    public Guid Id{ get; set; }
    public string BookName{ get; set; }
    public virtual ICollection<BookPage> BookPages{ get; set; } 
}

 public class BookPage
 { 
        public Guid Id{ get; set; }
        public int PageNum{ get; set; }
        public string PageContent{ get; set; }
 }

You can write a query to get Book which not is referenced in BookPage:

var query = BookRepository
            .Include(x => x.BookPages)
            .Where(x => x.Id == input.Id && x.BookPages.Count == 0)
            .ProjectTo<BookDto>(ItemMapper);