WP7调用webservice程序卡住不动

Question

public  void sendMessage(string xmlstring)
{ 

            MsgService.MsgServiceSoap msgClient = new MsgService.MsgServiceSoapClient();
            IAsyncResult ar = msgClient.BeginSendMessage(xmlstring, null,null);
            ar.AsyncWaitHandle.WaitOne();
            stringdata = msgClient.EndSendMessage(ar);

}

void msgClient_SendMessageCompleted(object sender, MsgService.SendMessageCompletedEventArgs e)
{     

          if(e.Error!=null)

         {

             stringdata = e.Result;

         }

}

调用该方法的时候一直卡住不动，调试的时候发现一直卡在   ar.AsyncWaitHandle.WaitOne();  这一句这里。

求解决这个问题。