protected override bool ValidateAllFields()
        {
            string phoneNumber = StringUtils.RemoveNonIntegers(PhoneNumberTextField.Text.Trim());

            bool allFieldsValid = true;

            if (String.IsNullOrEmpty(phoneNumber) || phoneNumber.Length < 10 || phoneNumber.Length > 11)
            {
                PhoneNumberTextField.SetInvalid();
                allFieldsValid = false;
            }

            return(allFieldsValid);
        }
        async partial void ValidateButtonClicked(Foundation.NSObject sender)
        {
            View.EndEditing(true);

            string phoneNumber = StringUtils.RemoveNonIntegers(PhoneNumberTextField.Text.Trim());

            phoneNumber = StringUtils.RemoveLeadingSymbol(phoneNumber, "1");

            bool allFieldsValid = ValidateAllFields();

            if (!allFieldsValid)
            {
                return;
            }

            ShowHud(Strings.Hud.please_wait);

            try
            {
                var result = await TwilioServices.StartPhoneVerificationAsync(phoneNumber);

                if (result != null && result.success && result.is_cellphone)
                {
                    var vc = new EnterPhoneNumberVerificationCodeViewController();
                    vc.PhoneNumber = phoneNumber;
                    NavigationController.PushViewController(vc, true);
                }
                else
                {
                    PhoneNumberTextField.SetInvalid();
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                Console.WriteLine(e.StackTrace);
            }

            HideHud();
        }