public void CloseCenter()
        {
            Console.WriteLine("Center closing ...");
            Thread.Sleep(3000);

            // Call all the callback functions registered
            CenterClosed?.Invoke(this, new CenterEventArgs {
                Center = this
            });
        }
 protected virtual void OnCenterClosed()
 {
     CenterClosed?.Invoke(this, new CenterEventArgs {
         Center = this
     });
 }