text: public virtual Tuple<string, string> SplitExtensionField(string defaultField, string field){int indexOf = field.IndexOf(this.extensionFieldDelimiter);if (indexOf < 0)return new Tuple<string, string>(field, null);string indexField = indexOf == 0 ? defaultField : field.Substring(0, indexOf);string extensionKey = field.Substring(indexOf + 1);return new Tuple<string, string>(indexField, extensionKey);}