/// <summary>
        /// Hides the dialog window
        /// </summary>
        /// <param name="windowContents">Contents of the window displayed earlier using ShowWindow</param>
        public void HideWindow(FrameworkElement windowContents)
        {
            if (windowContents == null)
            {
                throw new ArgumentNullException("windowContents");
            }

            int            hashCode       = windowContents.GetHashCode();
            FloatingWindow floatingWindow = null;

            if (m_FloatingWindows.TryGetValue(hashCode, out floatingWindow))
            {
                floatingWindow.Hide();
                // close will automatically remove the window from the hash table in floatingWindow_Closed
            }
        }