public async void Button_Clicked(object sender, EventArgs e)
{
var currencyFrom = pickerConvertFrom.Items[pickerConvertFrom.SelectedIndex];
var currencyTo = pickerConvertTo.Items[pickerConvertTo.SelectedIndex];
var exchangeAmount = int.Parse(txtCurrencyAmount.Text);
var exchangeRates = await _exchangeRateService.GetExchangeRates(currencyFrom, currencyTo);
var exchangeTo = _exchangeRateService.countriesDictionary[currencyTo];
var rate = exchangeRates.rates[exchangeTo];
var amount = _exchangeRateService.CaculateExchangeRate(exchangeAmount, rate).ToString();
var message = $"{exchangeAmount} {currencyFrom} = $ {amount} {exchangeTo} ";
lblexchangedAmount.Text = amount.ToString();
}