Vehicle/WPF01/MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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 WPF01
{
    /// <summary>
    /// Логика взаимодействия для MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void ButtonClick(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("Hello World");
        }

        private void TextBoxInput(object sender, KeyEventArgs e)
        {
           if (textBoxLogin.Text.Length >= 4 && textBoxPassword.Password.Length >= 4)
            {
                buttonLogin.IsEnabled = true;
            }
            else
            {
                buttonLogin.IsEnabled = false;
            }
        }

    }
}