Table relations of the EF model error

Question

User-767136372 posted

Good day, I'm new to ASP.NET MVC and I'm trying to make a simple application where I only have two tables, the first table is the author and the second is the table books. When I register an author, he saves it in the database, but when I want to register a book, he marks me an error.

System.Data.Entity.Infrastructure.DbUpdateException: 'An error occurred while updating the entries. See the inner exception for details.'

InvalidOperationException: A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'Id'.

I have a foreign key that refers to authors in the book table:

Id_autor int foreign key references autor(ID)

And this is the POST method

        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "Id,nombrelibro")] libros libros)
        {
            if (ModelState.IsValid)
            {
                db.libros.Add(libros);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.Id = new SelectList(db.autor, "Id", "nombre", libros.Id);
            return View(libros);
        }

I hope you can help me, thanks!

Answer 1

User1120430333 posted

See the inner exception for details.'

The inner exception is going to tell you what is wrong and why the program blew-up. Without you using a try/catch and looking at the inner exception, all you'll be doing is stabbing in the dark.

https://www.c-sharpcorner.com/uploadfile/puranindia/innerexception-in-C-Sharp/

Answer 2

User1520731567 posted

Hi simpleprogrammer,

When I register an author, he saves it in the database, but when I want to register a book, he marks me an error.

System.Data.Entity.Infrastructure.DbUpdateException: 'An error occurred while updating the entries. See the inner exception for details.'

InvalidOperationException: A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'Id'.

I have a foreign key that refers to authors in the book table:

Id_autor int foreign key references autor(ID)

According to your description,when you try to add the record there is a reference constraint violation. 

When you add a book record,you need to select a author id that clarify who this book belongs to.

I suggest you could add a scaffolded item to meet your needs quickly.

You could follow the steps below:

Right click on Controllers -> Choose Add -> Choose 'MVC5 Controller with views, using Entity Framework', then Add-> Choose the Model you want to add CRUD to in 'Model class', then Add -> The controller with CRUD function is created.

Then the  Index,Details,Edit,Create ..pages will be automatically generated.And compare with your code.

Actually,you could use one to many entity.

For example:

 public class author
    {
        public author()
        {
            book = new List<book>();
        }
        [Key]
        public int Author_id { get; set; }
        public string Name { get; set; }
        public List<book> book { get; set; }

    }

 public class book
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Publisher { get; set; }
        public int Author_id { get; set; }
        [ForeignKey("Author_id")]
        public virtual author author { get; set; }
    }

If you have any questions,please post more details,so that I can understand what your mean better.

Best Regards.

Yuki Tao