c# - AddRange throwing null exception -

i have function called getsuggestedaddresses , there's piece of calls function returns list. have property in class type list. tried using addrange add in returned results property throwing null exception. tried stepping through code i'm bit lost. ideas? here code-

 public list<expressaddressresult> getsuggestedaddresses(string format = "xml")   {      foreach (requestarrayrecord address in reqrecords) {         string result = string.empty;         namevaluecollection collection = new namevaluecollection();         collection.add("id", authkey);         collection.add("line1", cleanupaddress(address.addressline1));         collection.add("city", address.city);         collection.add("state", address.state);         collection.add("postalcode", address.zip);         collection.add("maxrecords", maxsuggestionresults.tostring());         collection.add("format", format);         string parameters = generateparameters(collection);          uri serviceaddress = new uri(requesturl + parameters);         httpwebrequest request = (httpwebrequest)webrequest.create(serviceaddress);         using (httpwebresponse response = (httpwebresponse)request.getresponse()) {            if (response != null) {               using (streamreader streamreader = new streamreader(response.getresponsestream())) {                  result = streamreader.readtoend();               }            }         }          xmldocument xmldoc = new xmldocument();         xmldoc.loadxml(result);          list<expressaddressresult> results = createlistfromxml(xmldoc);          if (results != null) {            addresssuggestions.addrange(results); // throws null exception         }      }       return addresssuggestions; // property of type list<expressaddressresult>   } 

var addresssuggestions = new list<expressaddressresult>(); 

though think want return results.. it's been converted expected type. forget addrange