Entity Framework Core Interview Question #35

What is an optional relationship in EF Core?

Relationships, Navigation Properties & Loading Data Junior Beginner

Quick Interview Answer

An optional relationship allows the dependent entity to exist without an associated principal. The foreign-key property is normally nullable.

Detailed Explanation

An optional relationship allows the dependent entity to exist without an associated principal. The foreign-key property is normally nullable.

For example, an Employee might optionally have a Manager. A nullable ManagerId represents the absence of that relationship.

Optional relationships should be modeled intentionally so null values have a clear business meaning.

Code Example

public class Employee
{
    public int Id { get; set; }

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