private async void signInButton_Clicked(object sender, EventArgs e)
        {
            try
            {
                var result = await _viewModel.SignIn();

                if (result.ResultCode == -1)
                {
                    await DisplayAlert("Error", result.ResultMessage, "OK");
                }
                else
                {
                    ResultPage resultPage = new ResultPage();
                    resultPage.Init(result);
                    await PopupNavigation.PushAsync(resultPage, true);
                }
            }
            catch (Exception ex)
            {
                await DisplayAlert("Error", ex.Message, "OK");
            }
        }