procedure TForm1.Button1Click(Sender: TObject);
begin
   if(RadioButton1.Checked) then
    DataModule2.SimpleDataSet1.SaveToFile('name')
  else
    DataModule2.SimpleDataSet1.SaveToFile('name.xml',dfXML);
end;编译时出错:[Error] Unit1.pas(41): Undeclared identifier: 'dfXML'
请问为何?谢谢!!