How to avoid exception of remote internal server 500 error on consuming a web service?

private void sample()
       {
           try

           {
               string requestUrl="http://ntp-434:95/WebService1.asmx?op=HelloWorld";

               WebRequest request = WebRequest.Create(requestUrl);
               // Set the Method property of the request to POST.
               request.Method = "POST";

               // Create POST data and convert it to a byte array.
               string postData = "This is a test that posts this string to a Web server.";
               byte[] byteArray = Encoding.UTF8.GetBytes(postData);
               // Set the ContentType property of the WebRequest.
               request.ContentType = "application/x-www-form-urlencoded";
               // Set the ContentLength property of the WebRequest.
               request.ContentLength = byteArray.Length;

               // Get the request stream.
               Stream dataStream = request.GetRequestStream();
               // Write the data to the request stream.
               dataStream.Write(byteArray, 0, byteArray.Length);
               // Close the Stream object.
               dataStream.Close();

               // Get the response.
               WebResponse response = request.GetResponse();
               // Display the status.
               Console.WriteLine(((HttpWebResponse)response).StatusDescription);
               // Get the stream containing content returned by the server.
               dataStream = response.GetResponseStream();
               // Open the stream using a StreamReader for easy access.
               StreamReader reader = new StreamReader(dataStream);
               // Read the content.
               string responseFromServer = reader.ReadToEnd();
               // Display the content.
               Console.WriteLine(responseFromServer);
               // Clean up the streams.
               reader.Close();
               dataStream.Close();
               response.Close();
           }
           catch(Exception ex)
           {

           }
       }