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次のコードを使用して、Windows 8 で Json 配列をダウンロードできます。

aString = " http://website.com/image/image_manifest.json ";

private async void GetJSON(string aString)
        {
            var client = new HttpClient();
            var lResponse = await client.GetStringAsync(aString);
}

これは100％機能します

私はこれを使ってWindows phoneで同じことをしようとしています

        private void GetJSON(string aNASAURL)
        {
            WebClient webClient = new WebClient();
            webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(webClientHandler);
              webClient.DownloadStringAsync(new Uri(aString));
}
    private void webClientHandler(object sender, DownloadStringCompletedEventArgs e)
        {
            var lResponse = e.Result;
}

これは機能しません。次の例外が発生します。

タイプ 'System.Reflection.TargetInvocationException' の例外が System.ni.dll で発生しましたが、ユーザー コードで処理されませんでした

内部例外に入ると、次のようになります。

InnerException {System.Net.WebException: リモート サーバーがエラーを返しました: NotFound. ---> System.Net.WebException: リモート サーバーがエラーを返しました: NotFound。

以下の完全な例外。

編集: HttpClient クラスは Windows Phone では使用できません。interwebs の提案に従って WebClient を選択しました。他のオプションを開きます。await メソッドが機能していないようで、WebClient を Async と呼ぶ必要があります。文字列からURIへの変換に関係があるのではないかと思います。残念ながら、URL はまだ公開できませんが、文字列と同様の URL 構造を次に示します。

わかりやすくするために編集......

> -     e   {System.Net.DownloadStringCompletedEventArgs}   System.Net.DownloadStringCompletedEventArgs
+       base    {System.Net.DownloadStringCompletedEventArgs}   System.ComponentModel.AsyncCompletedEventArgs {System.Net.DownloadStringCompletedEventArgs}
-       Result  'e.Result' threw an exception of type 'System.Reflection.TargetInvocationException' string {System.Reflection.TargetInvocationException}
-       base    {System.Reflection.TargetInvocationException: An exception occurred during the operation, making the result invalid.  Check InnerException for exception details. ---> System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound.
   at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)
   --- End of inner exception stack trace ---
   at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
   at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
   at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)
   --- End of inner exception stack trace ---
   at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()
   at System.Net.DownloadStringCompletedEventArgs.get_Result()} System.Exception {System.Reflection.TargetInvocationException}
+       Data    {System.Collections.ListDictionaryInternal} System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
        HelpLink    null    string
        HResult -2146232828 int
-       InnerException  {System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound.
   at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)
   --- End of inner exception stack trace ---
   at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
   at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
   at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)}   System.Exception {System.Net.WebException}
+       [System.Net.WebException]   {System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound.
   at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)
   --- End of inner exception stack trace ---
   at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
   at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
   at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)}   System.Net.WebException
+       Data    {System.Collections.ListDictionaryInternal} System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
        HelpLink    null    string
        HResult -2146233079 int
-       InnerException  {System.Net.WebException: The remote server returned an error: NotFound.
   at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)}  System.Exception {System.Net.WebException}
+       [System.Net.WebException]   {System.Net.WebException: The remote server returned an error: NotFound.
   at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)}  System.Net.WebException
+       Data    {System.Collections.ListDictionaryInternal} System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
        HelpLink    null    string
        HResult -2146233079 int
+       InnerException  null    System.Exception
        Message "The remote server returned an error: NotFound."    string
        Source  "System.Windows"    string
        StackTrace  "   at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)\r\n   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)\r\n   at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)"    string
+       Static members      
+       Non-Public members      
        Message "The remote server returned an error: NotFound."    string
        Source  "System.Windows"    string
        StackTrace  "   at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)\r\n   at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)\r\n   at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)\r\n   at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)"  string
+       Static members      
+       Non-Public members      
        Message "An exception occurred during the operation, making the result invalid.  Check InnerException for exception details."   string
        Source  "System"    string
        StackTrace  "   at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()\r\n   at System.Net.DownloadStringCompletedEventArgs.get_Result()" string
+       Static members      
+       Non-Public members
4

2 に答える 2

1

DownloadStringTaskAsyncJon Skeet が提案したような関数を書くことができます。

WebClient wc = new WebClient();
string result = await wc.DownloadAsync("http://www.stackoverflow.com");

public static partial class MyExtensions
{
    public static Task<string> DownloadAsync(this WebClient wc, string url)
    {
        TaskCompletionSource<string> tcs = new TaskCompletionSource<string>();
        DownloadStringCompletedEventHandler completed = null;

        completed = (s, e) =>
        {
            try
            {
                tcs.SetResult(e.Result);
            }
            catch (Exception ex)
            {
                tcs.SetException(ex.InnerException ?? ex);
            }
            finally
            {
                wc.DownloadStringCompleted -= completed;
            }
        };

        wc.Headers[HttpRequestHeader.UserAgent] = "Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.12) Gecko/20101026 Firefox/3.6.12";
        wc.DownloadStringCompleted += completed;
        wc.DownloadStringAsync(new Uri(url));

        return tcs.Task;
    }
}
于 2013-05-04T09:57:12.780 に答える