MainActivity_OnStart.cs

protected override void OnStart()
{
    base.OnStart();
    RefreshUserInputsFromVariables();
}
// ...
private void RefreshUserInputsFromVariables()
{
    _inputAmount.SetText(_amount.ToString(CultureInfo.InvariantCulture), TextView.BufferType.Editable);
    _txtResultDecimal.SetText(_result.ToString(CultureInfo.InvariantCulture), TextView.BufferType.Editable);
    _inputNumberOfPeople.SetText(_numberOfPeople.ToString(CultureInfo.InvariantCulture),
        TextView.BufferType.Editable);
}