Getting a list of posting periods

@operator

I am trying to get a list of all the open posting periods. I am using 2009.2.0 and c#.

private static BaseRef[] GetPostingPeriod()
    {
        GetSelectValueFieldDescription selectValueField = new GetSelectValueFieldDescription();
        selectValueField.recordType = RecordType.accountingPeriod;
        selectValueField.recordTypeSpecified = true;
        selectValueField.field = "name";
        GetSelectValueFilter getSelectValueFilter = new GetSelectValueFilter();
        getSelectValueFilter.@operator = GetSelectValueFilterOperator.contains;
        getSelectValueFilter.filterValue = "";
        selectValueField.filter = getSelectValueFilter;
        GetSelectValueResult selectValueResult = _netSuiteService.getSelectValue(selectValueField,1);
        return selectValueResult.baseRefList;
    }

I keep getting null results and can not figure out why. _netSuiteService is my NetSuiteService.