调用.net的webservice,该如何解决

private String ws(){        String result="";        try{            SoapObject request=new SoapObject(NAMESPACE,MEHTODNAME);//NameSpace                        request.addProperty("i","5");            request.addProperty("j", "6");                        SoapSerializationEnvelope envelope=new SoapSerializationEnvelope(                    SoapEnvelope.VER11);                        envelope.dotNet=true;                        envelope.setOutputSoapObject(request);                        HttpTransportSE ht=new HttpTransportSE(URL);                        [color=#FF0000]ht.call(SOAPACTION, envelope);[/color]    //到这一步就异常 找不到原因                      if(envelope.getResponse()!=null){                SoapPrimitive response=(SoapPrimitive)envelope.getResponse();                result=response.toString();            }                    }catch(Exception e){            result=e.getMessage();        }        return result;    }