Practical approach to Memento design pattern

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace MementoPattern
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Employee _emp;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            _emp = new Employee("Praveen", "Raghuvanshi", 1);
            this.buttonUndo.IsEnabled = this.buttonRedo.IsEnabled = false;
            Update();
        }
        
        private void buttonSave_Click(object sender, RoutedEventArgs e)
        {
            Save();
        }

        private void buttonCancel_Click(object sender, RoutedEventArgs e)
        {
            Revert();
        }

        private void buttonUndo_Click(object sender, RoutedEventArgs e)
        {
            SaveAndUpdateState();
            EnableUndo(false);
        }

        private void buttonRedo_Click(object sender, RoutedEventArgs e)
        {
            SaveAndUpdateState();
            EnableUndo(true);
        }

        private void Update()
        {
            textBoxFirstName.Text = _emp.FirstName;
            textBoxLastName.Text = _emp.LastName;
            textBoxId.Text = _emp.Id.ToString();
        }

        private void Save()
        {
            CareTaker.Instance.EmployeeMemento = _emp.SaveEmployee();

            _emp.FirstName = textBoxFirstName.Text;
            _emp.LastName = textBoxLastName.Text;
            _emp.Id = Convert.ToUInt16(textBoxId.Text);
            
            // Reset the undo/redo button
            EnableUndo(true);
        }

        private void Revert()
        {
            Update();
        }

        private void SaveAndUpdateState()
        {
            var empMemento = _emp.SaveEmployee();
            _emp.RestoreEmployee(CareTaker.Instance.EmployeeMemento);
            Update();
            CareTaker.Instance.EmployeeMemento = empMemento;
        }

        private void EnableUndo(bool isEnableUndo)
        {
            this.buttonUndo.IsEnabled = isEnableUndo;
            this.buttonRedo.IsEnabled = !isEnableUndo;
        }
    }
}