我正在研究Wp8 app.On Phone测试Always Send System.Reflection.TargetInvocationException

Question

我正在开发窗口手机应用程序。当我在App Emulator上测试时它工作完全正常。但是如果我在手机上测试这个应用程序，它总是发给我System.Reflection.TargetInvocationExceptipon。

WebClient webClient = new WebClient();
webClient.DownloadStringCompleted += jobseeker;
//ProgressBarRequest.Visibility = System.Windows.Visibility.Visible;
webClient.DownloadStringAsync(new Uri(string.Format("http://ec2-54-66-100-115.ap-southeast-2.compute.amazonaws.com/jjhj/abvsfss.php?func=login&Username={0}&Password={1}&cachebust=", txtUserName.Text, txtpswd.Password,DateTime.Now)));