// Process the SOAP message received and write to a log file.
public override void ProcessMessage(SoapMessage message) 
{
   switch (message.Stage) 
   {
      case SoapMessageStage.BeforeSerialize:
         break;
      case SoapMessageStage.AfterSerialize:
         WriteOutput((SoapClientMessage)message);
         break;
      case SoapMessageStage.BeforeDeserialize:
         WriteInput((SoapClientMessage)message);
         break;
      case SoapMessageStage.AfterDeserialize:
         break;
      default:
         throw new Exception("invalid stage");
   }
}

// Write the contents of the outgoing SOAP message to the log file.
public void WriteOutput(SoapClientMessage message)
{
   newStream.Position = 0;
   FileStream myFileStream = new FileStream(filename, FileMode.Append,
      FileAccess.Write);
   StreamWriter myStreamWriter = new StreamWriter(myFileStream);
   myStreamWriter.WriteLine(
      "================================== Request at "
      + DateTime.Now);

   // Print to the log file the request header field for SoapAction header.
   myStreamWriter.WriteLine("The SoapAction Http request header field is: ");
   myStreamWriter.WriteLine("\t" + message.Action);

   // Print to the log file the type of the client that invoked 
   // the XML Web service method.
   myStreamWriter.WriteLine("The type of the client is: ");
   if((message.Client.GetType()).Equals(typeof(MathSvc)))
      myStreamWriter.WriteLine("\tMathSvc");

   // Print to the log file the method invoked by the client.
   myStreamWriter.WriteLine(
      "The method that has been invoked by the client is:");
   myStreamWriter.WriteLine("\t" + message.MethodInfo.Name);

   // Print to the log file if the method invoked is OneWay.
   if(message.OneWay)
      myStreamWriter.WriteLine(
        "The client doesn't wait for the server to finish processing");
   else
      myStreamWriter.WriteLine(
        "The client waits for the server to finish processing");

   // Print to the log file the URL of the site that provides 
   // implementation of the method.
   myStreamWriter.WriteLine(
      "The URL of the XML Web service method that has been requested is: ");
   myStreamWriter.WriteLine("\t" + message.Url);
   myStreamWriter.WriteLine("The contents of the SOAP envelope are: ");
   myStreamWriter.Flush();

   // Copy the contents of one stream to another. 
   Copy(newStream, myFileStream);
   myFileStream.Close();
   newStream.Position = 0;

   // Copy the contents of one stream to another. 
   Copy(newStream, oldStream);
}