System.Xml.Serialization.XmlSerializationWriter.GetId C# (CSharp) Method

        private string GetId(object o, bool addToReferencesList)
        {
            if (_references == null)
            {
                _references = new Hashtable();
                _referencesToWrite = new ArrayList();
            }
            string id = (string)_references[o];
            if (id == null)
            {
                id = _idBase + "id" + (++_nextId).ToString(CultureInfo.InvariantCulture);
                _references.Add(o, id);
                if (addToReferencesList) _referencesToWrite.Add(o);
            }
            return id;
        }