System.exception中的异常

Question

我目前正在开发Weather API，我正在尝试从OpenWeatherMap.org获取值。但是当我点击按钮从网站上检索信息时。它给了我以下错误。Here's the Screenshot of the exception,I am Getting.

此处还有我点击按钮的UI。

Here's the Screenshot

System.Exception was unhandled by user code
HResult=-2146233088
Message=Exception of type 'System.Exception' was thrown.
Source=UWPWeather
StackTrace:
   at UWPWeather.LocationManager.<GetPosition>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at UWPWeather.MainPage.<Button_Click>d__1.MoveNext()
   InnerException: 

OpenWeatherMapProxy.cs代码：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;
using System.Threading.Tasks;

namespace WeatherAPI
{
    public class OpenWeatherMapProxy
    {
        public async static Task<RootObject>GetWeather(double lat,double lon)
        {
            var http = new HttpClient();
            var response = await http.GetAsync("http://api.openweathermap.org/data/2.5/weather? lat=35&lon=77.20081&appid=b1b15e88fa797225412429c1c50c122a");

            var result = await response.Content.ReadAsStringAsync();

            var serializer = new DataContractJsonSerializer(typeof(RootObject));

            var ms = new MemoryStream(Encoding.UTF8.GetBytes(result));

            var data = (RootObject)serializer.ReadObject(ms);
            return data;
        }
    }

    public class Coord
    {
        [DataMember]
        public double lon { get; set; }
        [DataMember]
        public double lat { get; set; }
    }
    [DataContract]
    public class Weather
    {
        [DataMember]
        public int id { get; set; }
        [DataMember]
        public string main { get; set; }
        [DataMember]
        public string description { get; set; }
        [DataMember]
        public string icon { get; set; }
    }
    [DataContract]
    public class Main
    {
        [DataMember]
        public double temp { get; set; }
        [DataMember]
        public int pressure { get; set; }
        [DataMember]
        public int humidity { get; set; }
        [DataMember]
        public double temp_min { get; set; }
        [DataMember]
        public double temp_max { get; set; }
    }
    [DataContract]
    public class Wind
    {
        [DataMember]
        public double speed { get; set; }
        [DataMember]
        public int deg { get; set; }
    }
    [DataContract]
    public class Clouds
    {
        [DataMember]
        public int all { get; set; }
    }
    [DataContract]
    public class Sys
    {
        [DataMember]
        public int type { get; set; }
        [DataMember]
        public int id { get; set; }
        [DataMember]
        public double message { get; set; }
        [DataMember]
        public string country { get; set; }
        [DataMember]
        public int sunrise { get; set; }
        [DataMember]
        public int sunset { get; set; }
    }
    [DataContract]
    public class RootObject
    {
        [DataMember]
        public Coord coord { get; set; }
        [DataMember]
        public List<Weather> weather { get; set; }
        [DataMember]
        public string @base { get; set; }
        [DataMember]
        public Main main { get; set; }
        [DataMember]
        public Wind wind { get; set; }
        [DataMember]
        public Clouds clouds { get; set; }
        [DataMember]
        public int dt { get; set; }
        [DataMember]
        public Sys sys { get; set; }
        [DataMember]
        public int id { get; set; }
        [DataMember]
        public string name { get; set; }
        [DataMember]
        public int cod { get; set; }
    }
}

MainPage.xaml.cs代码：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The Blank Page item template is documented at           http://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace WeatherAPI
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private async void Button_Click(object sender, RoutedEventArgs e)
        {
            RootObject myWeather = await OpenWeatherMapProxy.GetWeather(20.0,30.0);
            ResultTextBlock.Text = myWeather.name + " - " + ((int)myWeather.main.temp).ToString();
        } 
    }
}