在.net中使用Mashape API的问题

我在网上找到了一些使用Mashape API获取QR码的很棒的代码。这里。

他们的代码工作得很好，但如果我试图改变它使用另一个Mashape，我得到一个

"操作过程中发生异常，导致该结果无效的"

错误。还有一些关于检查内部异常的内容。

下面的代码显示了来自链接的QR码，我尝试使用天气API和Spotify API。

private void Button_Click(object sender, RoutedEventArgs e)
{
    WebClient client = new WebClient();
    client.UploadStringCompleted += new UploadStringCompletedEventHandler(client_UploadStringCompleted);
    client.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
    client.Headers["X-Mashape-Authorization"] = "mashape-api-code-goes-here";
    StringBuilder postData = new StringBuilder();
    // For Spotify (this doesn't work)
    // postData.AppendFormat("{0}={1}", "q", HttpUtility.UrlEncode(txtArtitst.Text));
    // var uri = new Uri("https://mager-spotify-web.p.mashape.com/search/1/artist.json?", UriKind.Absolute);
    // For Weather info (this doesn't work)
    postData.AppendFormat("{0}={1}", "_method", HttpUtility.UrlEncode("getForecasts"));
    postData.AppendFormat("&{0}={1}", "location", HttpUtility.UrlEncode("brisbane"));
    var uri = new Uri("https://george-vustrey-weather.p.mashape.com/api.php?", UriKind.Absolute);
    // For QR Code (this works)
    //postData.AppendFormat("{0}={1}", "content", HttpUtility.UrlEncode("TestQRCode"));
    //postData.AppendFormat("&{0}={1}", "quality", HttpUtility.UrlEncode("L"));
    //postData.AppendFormat("&{0}={1}", "type", HttpUtility.UrlEncode("text"));
    //postData.AppendFormat("&{0}={1}", "size", HttpUtility.UrlEncode("5"));
    //var uri = new Uri("https://mutationevent-qr-code-generator.p.mashape.com/generate.php?", UriKind.Absolute);
    client.UploadStringAsync(uri, "POST", postData.ToString());
    txtResult.Text = postData.ToString();
    progress1.IsIndeterminate = true;
    button1.IsEnabled = false;
}

void client_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)
{
    progress1.IsIndeterminate = false;
    var client = sender as WebClient;
    client.UploadStringCompleted -= client_UploadStringCompleted;
    string response = string.Empty;
    if (!e.Cancelled)
    {
        try
        {
            response = HttpUtility.UrlDecode(e.Result);  // seems to error out here - result invalid
            txtResult.Text = response;
        }
        catch (Exception ex)
        {
            txtResult.Text = "ERROR : " + ex.Message;
        }
    }
    button1.IsEnabled = true;
}

内部异常说:

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}