Adding XML file to a SOAP request

I found out how to send a request to a webservice using ksoap, but i still cannot figure out where to add my XML to the request ! Here is my code :

    public static SoapObject soap () throws IOException, XmlPullParserException {
    SoapObject request = new SoapObject (NAMESPACE, METHOD_NAME);

    /* HERE IS THE PROBLEM */
    request.addProperty(toto, HERE IS MY XML);

    SoapSerializationEnvelope envelope = new SoapSerializationEnvelope (
            SoapEnvelope.VER11);
    envelope.setOutputSoapObject (request);
    HttpTransportSE androidHttpTransport = new HttpTransportSE (URL);
    androidHttpTransport.debug = true; 
    androidHttpTransport.call (SOAP_ACTION, envelope);
    SoapObject soapResult = (SoapObject) envelope.getResponse ();
    return soapResult;
}

If i delete the "request.addProperty line", it reaches the server, but it does nothing, because i need to send my XML. If someone know how to do that, it would definitely make my day !!

Thanks you for reading this !