public void Edit(object param)
        {
            SignUpWindow    SignUpWindow = new SignUpWindow();
            SignUpViewModel signUpVM     = new SignUpViewModel(SelectedUser, users);

            SignUpWindow.DataContext = signUpVM;
            App.Current.MainWindow.Close();
            App.Current.MainWindow = SignUpWindow;
            SignUpWindow.Show();
        }
        public void Add(object parameter)
        {
            SignUpWindow    signUpWindow = new SignUpWindow();
            SignUpViewModel signUpVM     = new SignUpViewModel(users);

            signUpWindow.DataContext = signUpVM;
            App.Current.MainWindow.Close();
            App.Current.MainWindow = signUpWindow;
            signUpWindow.Show();
        }
        public void SignUp(object param)
        {
            SignUpWindow    window   = new SignUpWindow();
            SignUpViewModel signUpVM = new SignUpViewModel();

            window.DataContext = signUpVM;
            App.Current.MainWindow.Close();
            App.Current.MainWindow = window;
            window.Show();
        }