3 tier - business layer objects

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C#

Hi everyone,
I´m doing a small project for work, and I´m struggling a bit on how to create BLL objects in relation to the Database.
I have 2 questions (so far ...):
- How to represent foreign keys?
I would like to be able to use the instances for some logic (Ex: Shipment.Dispatcher.Name )), but in order to bound it to a control or update it I need the id.

- How to deal with master details?
With the example _items, should I make it public?, create a get only property? other way?

As an example I have 3 tables: Clients, Shipments and Items
I thought in doing it as you see below but I´m not feelling confident ...

What I have tried:

public class Shipment : INotifyPropertyChanged
{
	private int _id;
	private int _dispatcher_id;
	private Client _dispatcher;
	private List<Item> _items;
	
	public int DispatcherID
    {
		get
        {
			return _dispatcher_id;
        }
        set
        {
            _dispatcher = new Custom(value);
            _dispatcher_id = _dispatcher.ID;
            NotifyPropertyChanged();
        }
    }

	public Client Dispatcher    
	{
		get
        {
			return _dispatcher;
        }
    }		
}

How would you do it?
Thank you for your time.