public LoginWindowViewModel()
        {
            Login = "";
            Password = "";

            LoginCommand = new RelayCommand(LoginFunc, CanLogin);
            CreateAccountCommand = new RelayCommand(RegisterFunc, (obj) => true);
        }
 MainWindowViewModel()
 {
     SaveXLS = new RelayCommand(SaveToXML,CanSave);
     LoadDB = new RelayCommand(Load, (obj) => true);
     Logout = new RelayCommand(LogoutFunc,(obj) => true);
 }