如何在Entity Framework中通过Fluent API设置层次结构

Question

I have a hierarchy of employees, which have boss and subordinates.

public class Employee
{
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual string Job { get; set; }
    public virtual Employee Boss { get; set; }
    public virtual ICollection<Employee> Subordinates { get; set; }
}

I tried to configure it as follows:

internal class EmployeeConfiguracao : EntityTypeConfiguration<Employee>
{
  public EmployeeConfiguracao()
  {
    HasOptional(p => p.Boss).WithMany(p => p.Subordinates).WillCascadeOnDelete(false);
  }
}

But the result of Add-Migration Init
Note that Boss is not-null but the is optional (president has no boss)

CreateTable(
    "dbo.Employees",
    c => new
        {
            Id = c.Int(nullable: false, identity: true),
            Name = c.String(nullable: false, maxLength: 90),
            Job = c.String(),
            Boss_Id = c.Int(),
        })
    .PrimaryKey(t => t.Id)
    .ForeignKey("dbo.Employees", t => t.Boss_Id)
    .Index(t => t.Boss_Id);

How to set up this hierarchy so that it can be employed without boss (as President)

Answer 1

If Boss should be nullable it should be defined like this:

Boss_Id = c.Int(nullable: false)

If it is setup like this:

Boss_Id = c.Int()

then default value for nullable will be used which is true, so it is as you wanted it to be.