Error Violation of PRIMARY KEY constraint – C#

July 3, 2023

I have a problem with inserting data into a list. The error tells me that the Editor class cannot contain 2 identical Ids. I understand the error, but I’m not touching that class, just adding an object to the Books list. Here are my relations :

public class Author
{
    [Key]
    public int AuthorID { get; set; }

    public virtual Editor Editor { get; set; }

    public virtual ICollection<Book> Books { get; set; }
}

public class Book
{
    [Key]
    public int BookID { get; set; }

    [ForeignKey("Author")]
    public int AuthorID { get; set; }

    public virtual Author Author { get; set; }
}

public class Editor
{
    [Key, ForeignKey("Author")]
    public int AuthorID { get; set; }

    public virtual Author Author { get; set; }
}

Here is my addition :

Author Author = DBContext.Authors.FirstOrDefault(a => a.AuthorID == AuthorID);

Book Book = new Book
{
};

Author.Books.Add(Book);

DBContext.SaveChanges();

Here is the error :

SqlException: Violation of PRIMARY KEY constraint ‘PK_dbo.Editor’. Cannot insert duplicate key in object ‘dbo.Editor’. The duplicate key value is (89).

For reasons, I modified the classes but it is the same relations.
Thank you!

I tried rebuilding the tables and changing the relationships. However, when I changed Editor’s relationship, instead of giving me an error, it was creating empty Books from it, the last one was linked to the Author and the other ones were delinked.

>Solution :

Try following class structure

public class Author
{
    [Key]
    public int AuthorID { get; set; }

    public virtual Editor Editor { get; set; }

    public virtual ICollection<Book> Books { get; set; }
}

public class Book
{
    [Key]
    public int BookID { get; set; }

    [ForeignKey("Author")]
    public int AuthorID { get; set; }

    public virtual Author Author { get; set; }
}

public class Editor
{
    [Key]
    public int EditorID { get; set; }

    [ForeignKey("Author")]
    public int AuthorID { get; set; }

    public virtual Author Author { get; set; }
}

I believe Key (Ids) are Autogenerated.