Enviar Objeto como parametro para WS KSOAP2 [Android]

package br.com.sky.persistencia;

import java.util.ArrayList;
import java.util.List;

import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;
import br.com.sky.modelo.Materias;
import br.com.sky.modelo.ParametrosMateria;



public class ListarMateriasWS {
	private static final String SOAP_ACTION ="http://tempuri.org/IService1/ListarMaterias";
	private static final String METHOD_NAME ="ListarMaterias";
	private static final String NAMESPACE="http://tempuri.org/";
	private static final String URL="http://192.168.1.172/Service1.svc";

	List<Materias>listaMaterias =new ArrayList<Materias>();
	SoapObject result;

	
	public List<Materias> listarMaterias(ParametrosMateria parametros){		
		SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);		
		request.addProperty("ParametrosMateria", parametros);
		request.addProperty("token", "");
		SoapSerializationEnvelope envelope =new SoapSerializationEnvelope(SoapEnvelope.VER11);
		envelope.dotNet=true;
		envelope.setOutputSoapObject(request);	
		envelope.addMapping(NAMESPACE, ParametrosMateria.class.getSimpleName(), ParametrosMateria.class);
		try{
			HttpTransportSE androidHttpTranport = new HttpTransportSE(URL);
			androidHttpTranport.call(SOAP_ACTION, envelope);
			result 	= (SoapObject)envelope.getResponse();
			
			if(result != null){
				for (int i = 0; i < result.getPropertyCount(); i++) {
					listaMaterias.add(new Materias((SoapObject)result.getProperty(i)));
				}
			}
			
		}catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
		return listaMaterias;
	}
}