为什么我需要在子类中使用EF5的虚拟属性？

Question

I am using Entity Framework 5 with Code First and lazy loading disabled. Given the following:

public class Department
{
    public int DepartmentID { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Course> Courses { get; set; }
}

public class Course
{
    public int CourseID { get; set; }
    public string Title { get; set; }
    public int Credits { get; set; }
    public int DepartmentID { get; set; }
    public virtual Department Department { get; set; }
}

// Mapping Relationships for Course

<code here>
this.HasRequired(t => t.Department)
.WithMany(t => t.Courses)
.HasForeignKey(d => d.DepartmentID);

Can someone explain why I would need to have the:

public virtual Department Department { get; set; }

What would happen if I completely remove this line ? What would I not be able to do? As far as I can see the only thing I could not do is to use Entity Framework to check my foreign key. However I already have this set up in the database so I would still get an error from the Db.

Answer 1

The Department property exists as a link to a specific department for a course. It can be part of a one to many relationship which gives you access to a department from a course.

Answer 2

It contains your Department information, Depertment Name Courses information.I think you can remove it because the information of Department you can also access by searching for its DepartmentID . But it would be better to keep it.