Класс Employee для Антона (тема 10)

using System;
using System.Collections.Generic;
using System.Text;

namespace Task2
{
    public class Employee : User, IEquatable<Employee>
    {
        private string _title;
        private DateTime _hireDate;

        public int Experience
        {
            get
            {
                TimeSpan timeSpan = DateTime.Now - _hireDate;
                return (int)(timeSpan.TotalDays / 364.75);
            }
        }

        public string Title
        {
            get => _title;
            set
            {
                if (value == null)
                    throw new ArgumentNullException("Должность не может быть null");
                if (value.Length < 1)
                    throw new ArgumentException("Должность не может быть пустой!");

                _title = new string(value);
            }
        }

        public Employee(DateTime dateOfBirth, string name, string lastName, string patronymic, string title, DateTime hireDate)
            : base(dateOfBirth, name, lastName, patronymic)
        {
            if (hireDate > DateTime.Now)
                throw new ArgumentException("Данный пользователь ещё не мог быть нанят!");

            Title = title;
            _hireDate = hireDate;
        }

        public override string ToString() =>
            base.ToString() +
            "должность: " + Title + "\n" +
            "опыт: " + Experience + " года\n" +
            "нанят:" + _hireDate + "\n";

        public bool Equals(Employee other)
        {
            if (other is null)
                return false;

            if (ReferenceEquals(this, other))
                return true;

            if (this.GetType() != other.GetType())
                return false;

            return (base.Equals(other) && this.Experience == other.Experience
                && this.Title == other.Title);
        }

        public override bool Equals(object obj)
        {
            if (obj is null)
                return false;

            if (ReferenceEquals(this, obj))
                return true;

            if (this.GetType() != obj.GetType())
                return false;

            return this.Equals(obj as Employee);
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(base.GetHashCode(), Experience, Title);
        }

        public static bool operator ==(Employee employee1, Employee employee2)
        {
            if (employee1 is null || employee2 is null)
                return false;

            return employee1.Equals(employee2);
        }

        public static bool operator !=(Employee employee1, Employee employee2)
        {
            return !(employee1 == employee2);
        }
    }
}