Author.cs
Apply the same steps for creating
Book.cs to create the model file Author.cs:
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using System.ComponentModel.DataAnnotations;
namespace BookStore3.Models {
// Dependent (child)
public class Author {
[ Key ]
[ Required ]
public int Id { get; set; }
[ Display( Name = "Author Name" ) ]
[ Required ]
public string Name { get; set; }
// Foreign key property
public int BookId { get; set; }
// Reference navigation property
public Book? Book { get; set; }
}
}
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This one-to-many relationship is discovered by convention:
Bookis discovered as the principal in the relationship, andAuthoris discovered as the dependent.Author.BookIdis discovered as a foreign key of the dependent referencing theBook.Idprimary key of the principal. The relationship is discovered as required becauseAuthor.BookIdis not nullable.Book.Authorsis discovered as the collection navigation.Author.Bookis discovered as the reference navigation.
- One or more primary key properties on the principal entity; that is the “one” end of the relationship; e.g.,
Book.Id. - One or more foreign key properties on the dependent entity; that is the “many” end of the relationship; e.g.,
Author.BookId. - Optionally, a collection navigation on the principal entity referencing the dependent entities; e.g.,
Book.Authors. - Optionally, a reference navigation on the dependent entity referencing the principal entity; e.g.,
Author.Book.
- The foreign key property
Author.BookIdis not nullable. This makes the relationship “required” because every dependent (Author) must be related to some principal (Book), since its foreign key property must be set to some value. - Both entities have navigations pointing to the related entity or entities on the other side of the relationship.
using System.ComponentModel.DataAnnotations;-
The namespace provides attribute classes that are used to define metadata for ASP.NET MVC and ASP.NET data controls.
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President Lincoln was approached by a woman after a political speech… If you were my husband I would poison your tea. Lincoln replied...if you are my wife I’ll gladly drink it. |