private async void ToolbarItem_Clicked_Rename(object sender, EventArgs e)
        {
            var options = new ObservableCollection <EntryWithOptionViewModel.EntryWithOptionViewModelEntry>();

            if (!string.IsNullOrEmpty(Model.WordbookTitleUser) && Model.WordbookTitleUser != Model.WordbookTitleHtml)
            {
                var item = new EntryWithOptionViewModel.EntryWithOptionViewModelEntry(Model.WordbookTitleUser, Model.WordbookTitleUser);
                options.Add(item);
            }
            if (!string.IsNullOrEmpty(Model.WordbookTitleHtml))
            {
                var item = new EntryWithOptionViewModel.EntryWithOptionViewModelEntry(Model.WordbookTitleHtml, Model.WordbookTitleHtml);
                options.Add(item);
            }
            foreach (var item in RemoteStorage.GetNameSuggestions(Model.Uri))
            {
                if (item != Model.WordbookTitleUser)
                {
                    options.Add(new EntryWithOptionViewModel.EntryWithOptionViewModelEntry(item, item));
                }
            }
            if (Model == null)
            {
                return;
            }
            var vm         = (new EntryWithOptionViewModel(AppResources.WordbookRenameMessage, options, Model.WordbookTitle));
            var page       = new EntryWithOptionPage(vm);
            var waitHandle = new System.Threading.EventWaitHandle(false, System.Threading.EventResetMode.AutoReset);

            page.Disappearing += (s, e2) => waitHandle.Set();
            await Navigation.PushAsync(page);

            await Task.Run(() => waitHandle.WaitOne());

            var tmp = vm.GetValue <string>();

            if (tmp.Item2)
            {
                Model.WordbookTitleUser = tmp.Item1;
                await WordbooksImpressStorage.SaveLocalData();
            }
        }
        private async void ToolbarItem_Clicked_Delete(object sender, EventArgs e)
        {
            if (Model.HasMultipleWordbook)
            {
                await DisplayAlert(AppResources.WordWarning, AppResources.WordbookAlertCannotDelete, AppResources.AlertConfirmed);

                return;
            }
            var alertResult = await DisplayAlert(AppResources.WordWarning, AppResources.WordbookAlertConfirmDelete, AppResources.AlertYes, AppResources.AlertNo);

            if (!alertResult)
            {
                return;
            }
            WordbooksImpressStorage.Content.Remove(Model.Wordbooks[0]);
            await WordbooksImpressStorage.SaveLocalData();

            //認証情報を削除するか。迷うが削除しない事にする。
            //WordbooksImpressInfoStorage.Content.RemoveAll((w) => w.Url == Model.Wordbook.Uri);
            //WordsPageSemaphore.Dispose();
            await Navigation.PopAsync();
        }