C # – Web Api – Is it wrong to get a linked object like this?

I started developing with Api Web (asp.net Core) and I have a doubt about what is right or wrong in what I do …

I have two courses in 1 for N:

The department class:

public class
{
public int Id {get; together; }
public string Name {get; together; }
ICollection public Vendors {get; together; } = new list();
}

And the seller class:

public class Seller
{
public int Id {get; together; }
public string Name {get; together; }
public channel Email {get; together; }
public DateTime BirthDate {get; together; }
public double BaseSalary {get; together; }
Department Public Department {get; together; }
public int DepartmentId {get; together; }
ICollection public Sales {get; together; }
}

And I have a third class called DpId that inherits from Seller and has an Int:

Public class DpId: Seller
{
public int dpId {get; together; }

}

My question now appears:

I have a controller for the vendor where, in the publishing method, I proceed as follows to be able to register a vendor:

 [HttpPost]
 
 
 
 public actionResult insertSeller (DpId element)
{
item.Department = _dpService.findById (item.dpId);
_sellerService.insert (item);
returns NoContent ();
}

As you can see, to register a seller, I get the department for the class of sellers using dpId that went into the setting and then I registered.

Is it wrong? Is it better?

I started playing with Web Api not long ago, so I had a good tutorial that I could succeed (I've already seen the docs.microsoft web API tutorial)