將點擊選單後，會將選單關閉的事件寫入

MainPage.xaml.cs

        private void pageTitle_Click_1(object sender, RoutedEventArgs e)
        {
            // 若是第一次按，則將物件新增到 Popup 物件裡。
            if (!this.isAddedToPopup)
            {
                this.headerMenuPopup = ShowPopup(this.pageTitle, this.headerMenuCtl);
                this.headerMenuCtl.Tapped += headerMenuCtl_Tapped;
                this.isAddedToPopup = true;
            }
            // 顯示 Popup
            this.headerMenuPopup.IsOpen = true;
        }

        void headerMenuCtl_Tapped(object sender, TappedRoutedEventArgs e)
        {
            this.headerMenuPopup.IsOpen = false;
        }