请帮我查一个错误错误是：underclare identifier :'tupdaterecordtypes'，书上是叫我打开表将他的updaterecordtypes属性设为rtinserted,

procedure TForm2.FormActivate(Sender: TObject);
 var
   updrectypes:tupdaterecordtypes;
begin
studen:= mydata.dsstudent.dataset as tdbdataset;
gradetable:=mydata.ddsgrade.dataset as tdbdataset;
studenttable.close;
studenttable.open;
updrectypes:=[rtinserted];
studenttable.updatarecordtypes:=updrectypes;
cbgrade.text:='';
end;