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我一直在努力了一段時間，但我無法得到這項工作。我試圖通過使用'sort of'async await來下載一個json字符串到我的Windows Phone 8應用程序。我正在使用the promising solution of Matthias Shapiro。無法讓異步（異步等待）下載的JSON工作
HttpExtensions.cs
public static class HttpExtensions
{
public static Task<Stream> GetRequestStreamAsync(this HttpWebRequest request)
{
var taskComplete = new TaskCompletionSource<Stream>();
request.BeginGetRequestStream(ar =>
{
Stream requestStream = request.EndGetRequestStream(ar);
taskComplete.TrySetResult(requestStream);
}, request);
return taskComplete.Task;
}
public static Task<HttpWebResponse> GetResponseAsync(this HttpWebRequest request)
{
var taskComplete = new TaskCompletionSource<HttpWebResponse>();
request.BeginGetResponse(asyncResponse =>
{
try
{
HttpWebRequest responseRequest = (HttpWebRequest)asyncResponse.AsyncState;
HttpWebResponse someResponse = (HttpWebResponse)responseRequest.EndGetResponse(asyncResponse);
taskComplete.TrySetResult(someResponse);
}
catch (WebException webExc)
{
HttpWebResponse failedResponse = (HttpWebResponse)webExc.Response;
taskComplete.TrySetResult(failedResponse);
}
}, request);
return taskComplete.Task;
}
}
public static class HttpMethod
{
public static string Head { get { return "HEAD"; } }
public static string Post { get { return "POST"; } }
public static string Put { get { return "PUT"; } }
public static string Get { get { return "GET"; } }
public static string Delete { get { return "DELETE"; } }
public static string Trace { get { return "TRACE"; } }
public static string Options { get { return "OPTIONS"; } }
public static string Connect { get { return "CONNECT"; } }
public static string Patch { get { return "PATCH"; } }
}
而且我MainPageViewModel.cs
protected override void OnActivate()
{
base.OnActivate();
GetSessions();
}
private async void GetSessions()
{
var result = await GetMyData("http://localhost/api/MyData");
}
public async Task<string> GetMyData(string urlToCall)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlToCall);
request.Method = HttpMethod.Get;
HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
using (var sr = new StreamReader(response.GetResponseStream()))
{
return sr.ReadToEnd();
}
}
一旦碰到 「HttpWebResponse someResponse =（HttpWebResponse）responseRequest.EndGetResponse（asyncResponse）;」，我越來越a WebException：
「System.Net.WebException：遠程服務器返回錯誤：NotFound」
當我深入一點時，我注意到這個錯誤不是實際的錯誤。當我檢查在HttpExtensions類的GetResponseAsync方法裏面的「asyncResponse」我注意到該錯誤：
「AsyncWaitHandle =‘asyncResponse.AsyncWaitHandle’投擲‘System.NotSupportedException’類型的異常」
我沒有想法如何獲得這項工作。這是我做錯了什麼嗎？
奇怪的是，我使用完全相同，它的工作對我來說很好。你有沒有導入這個參考http://nuget.org/packages/Microsoft.Bcl.Async？ – robertk 2013-03-04 12:55:09
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