Object Composition Over Inheritance

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;

namespace WrongInheritance.ClassesAndInterfaces
{
    public class MainViewModel : INotifyPropertyChanged
    {
        private string selectedEmployeeType;
        private List<string> employeeTypes;
        private UserBase employee;

        public string SelectedEmployeeType
        {
            get
            {
                return selectedEmployeeType;
            }
            set
            {
                selectedEmployeeType = value;
                OnPropertyChanged("SelectedEmployeeType");
                OnEmployeeSelected();
            }
        }

        public List<string> EmployeeTypes
        {
            get
            {
                return employeeTypes;
            }
            set
            {
                employeeTypes = value;
                OnPropertyChanged("EmployeeTypes");
            }
        }

        public UserBase Employee
        {
            get
            {
                return employee;
            }
            set
            {
                employee = value;
                OnPropertyChanged("Employee");
            }
        }
        #region INotifyPropertyChanged Members

        public MainViewModel()
        {
            employeeTypes = new List<string> { "Manager", "Leader", "Coder" };
            selectedEmployeeType = "Manager";
            Employee = new Manager();
        }

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #endregion

        private void OnEmployeeSelected()
        {
            if (!string.IsNullOrEmpty(selectedEmployeeType))
            {
                switch (selectedEmployeeType)
                {
                    case "Manager":
                        Employee = new Manager();
                        break;
                    case "Leader":
                        Employee = new Leader();
                        break;
                    case "Coder":
                        Employee = new Coder();
                        break;
                }
            }
        }
    }
}