How do I override the the dialog box corner "X"? - Continued

To prevent the dialog box from closing when clicking the "X" button in the corner, you can handle the Closing event of the Window and set the Cancel property of the CancelEventArgs parameter to true. Here's how you can do it in your dlgNumbers class:

public partial class dlgNumbers : Window
{
    //------------------------------
    public dlgNumbers()
    {
        InitializeComponent();
        Closing += dlgNumbers_Closing; // Attach the event handler
    }

    // Event handler for the Closing event
    private void dlgNumbers_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        e.Cancel = true; // Cancel the closing action
    }
    //------------------------------
}

With this code, clicking the "X" button will no longer close the dialog box. You can still provide a button to close the dialog box programmatically if needed.

Alternatively, if you want to hide the "X" button altogether, you can set the WindowStyle property of the window to None, which removes the standard window border including the close button. However, you'll need to provide a custom way for users to close the dialog box, such as adding a button within the dialog box interface.

public partial class dlgNumbers : Window
{
    //------------------------------
    public dlgNumbers()
    {
        InitializeComponent();
        WindowStyle = WindowStyle.None; // Hide the standard window border
    }
    //------------------------------
}

Choose the approach that best fits your application's requirements.