How to close a hidden window (WPF application)?

Question

In my application (WPF) i have this window:

public partial class Window1 : Window and in the Xaml x:Class="WpfApplication1.Window1"

Now, when i switch to and from the main to window 1 and back, i us the Visibility.Hidden and Visibility.Visible to hide them and make them show again to the user.

What i try to do now, is make a test button in the main window, that says: Close Window1. This window is hidden, but i really want to close it in the background. at first i though to just use the Window.Close(); but that does not seem to do the trick.

So, how should i do this in a correct way ? Thank you very much in advance.

EDIT 1 - making question more clear

To open the window1 in my Main window, i use this part

Window1 W1 = null; // Initialise Field.
  public void CalcTabel_Click(object sender, RoutedEventArgs e)
   {
    if (W1 == null)
    {
     W1 = new Window1();
     W1.Hoofdmenu = this;
     W1.checkLang();
     W1.Show();
    }
   else
    {
     W1.checkLang();
     W1.Visibility = Visibility.Visible;
    }
   this.Visibility = Visibility.Hidden;
   }

On window 1 there is a Back button, that has this snip-it of code in it (Where "Hoofdmenu" us the main window):

Hoofdmenu.updateStatistics();
Hoofdmenu.Visibility = Visibility.Visible;
this.Visibility = Visibility.Hidden;

But again, this time when standing in the main window (so window 1 is hidden) i want to close down that window 1. but using W1.Close() does not seem to work. So i am looking for a way to Close that window 1, not change its visibility.

EDIT 2 - Solution

So using W1.Close(); did not work, although a small change this.W1.Close(); did work in fact :)

Answer 1

You can create object of Form2 in window and intialize its visiblity to false.

On click of button you can simpliy say

public partial class MainWindow : Window
  {
    private Window1 window2;

    public MainWindow()
    {
      InitializeComponent();
      this.window2 = new Window1();

      this.window2.Show();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
      this.window2.Visibility = System.Windows.Visibility.Hidden;
    }
  }

to make it visible again