using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CompanyHierarchy
{

    public abstract class Person : IPerson
    {
         private int id;
         private string firstName;
         private string lastName;
        public Person(int personID, string personFirstName, string personLastName)
        {
            this.ID = personID;
            this.FirstName = personFirstName;
            this.LastName = personLastName;
        }
        public int ID
        {
            get
            {
                return this.id;
            }
            set
            {
                if (value < 0)
                {
                    throw new ArgumentOutOfRangeException("ID cannot be negative!");
                }
                this.id = value;
            }
        }

        public string FirstName
        {
            get
            {
                return this.firstName;
            }
            set
            {
                if (String.IsNullOrEmpty(value))
                {
                    throw new ArgumentNullException("First name cannot be empty!");
                }
                this.firstName = value;
            }
        }

        public string LastName
        {
            get
            {
                return this.lastName;
            }
            set
            {
                if (String.IsNullOrEmpty(value))
                {
                    throw new ArgumentNullException("Last name cannot be empty!");
                }
                this.lastName = value;
            }
        }
    }
}