public MainWindow()
        {
            InitializeComponent();
            AdditionalInitializeComponent();
            VisualInitializeComponent();

            var loginWindow = new LoginWindow();

            loginWindow.ShowDialog();

            if (!loginWindow.DialogResult.HasValue || loginWindow.DialogResult != true)
            {
                Close();
                return;
            }
            Login          = loginWindow.GetLogin();
            SideMenu.Login = Login;
            SideMenu.LvlVisual();
            TopMenu.Login = Login;
            TopMenu.LvlVisual();

            PageSwitcher.Switch(new StartPage()); // Страница по умолчанию
        }