public partial class MainPage : ContentPage
    {
        RestService restService;
        public MainPage()
        {
            InitializeComponent();
            restService = new RestService();
        }
        async void OnButtonClicked(object sender, EventArgs e)
        {
            if(!string.IsNullOrWhiteSpace(cityEntry.Text))
            {
                WeatherData weatherData = await restService.GetWeatherDataAsync(GenerateRequestUri(Constants.OpenWeatherMapEndpoint));
                BindingContext = weatherData;
            }
            string GenerateRequestUri(string endpoint)
            {
                string requestUri = endpoint;
                requestUri += $"?q={cityEntry.Text}";
                requestUri += "&units=imperial";
                requestUri += $"&APPID={Constants.OpenWeatherMapAPIKey}";
                return requestUri;
            }
        }
    }