SilverLight下用WebRequest异步调用WCF服务

The primary reason is that the browser plugin networking APIs only support
async calls on the UI thread.    This means we are blocked from supporting
sync requests on the UI thread.  (If we blocked on the UI thread,we would never get the response callback from the browser.)  Looking at an API friendliness,scenarios,and resourcing priority,we don’t support a “simulated” sync call on a background thread.

即UI线程如果被阻塞的话，是不能得到异步响应结果的。关于这个问题，有一个简单的通过WebRequest异步调用的示例如下

 

private void Button_Click(object sender,RoutedEventArgs e) { Uri endpoint = new Uri(urlstr); WebRequest request = WebRequest.Create(endpoint); request.BeginGetResponse(new AsyncCallback(ResponseReady),request); //“simulated” sync call : do something here to get response } void ResponseReady(IAsyncResult asyncResult) { WebRequest request = asyncResult.AsyncState as WebRequest; WebResponse response = request.EndGetResponse(asyncResult); using (Stream responseStream = response.GetResponseStream()) { StreamReader readStream = new StreamReader(responseStream,Encoding.UTF8); string response = readStream.ReadToEnd(); } }

另外：一定要同步得到响应的话，可以通过SilverLight调用Javascript实现，在Javascript中使用XMLHttpRequest类即可。