Question

There is an DataAnnotation attribute counterpart for the HasOptional method of the code-first fluent API?

I want to mark my property with attribute instead of using the fluent API.

This is my current model & OnModelCreating code:

public class Employee
{
  #region Properties

  public int EmployeeID { get; set; }
  public string FirstName { get; set; }
  public string LastName { get; set; }

  public int? ManagerID { get; set; }
  public Employee Manager { get; set; }

  #endregion
}

 protected override void OnModelCreating(DbModelBuilder modelBuilder)
  {
    modelBuilder.Entity<Employee>().
      HasOptional(e => e.Manager).
      WithMany().
      HasForeignKey(m => m.ManagerID);
  }

Thanks

Answer 1

No, such an attribute doesn’t exist (in contrast to the [Required] attribute). I think the reason is that it is not necessary because

• Your model doesn’t need a mapping at all because conventions should detect the foreign key and also that the relationship is optional (because the FK property is nullable)
• If you would not have a foreign key property in your model, the relatonship is always optional because navigation references without exposed foreign key are always optional by default. Here the [Required] attribute would be necessary to make the relationship required.
• If your foreign key property would not be nullable, an optional relationship is not allowed.

So, there doesn’t seem to be a need for such an attribute (unless perhaps to make the optional relationship explicit in the class definition, but a comment above the property would do the same).