正確的刪除檔案步驟

procedure TForm1.Button1Click(Sender: TObject);
bDelete : boolean;
i : integer;
filename : string;
begin
  filename := 'C:\1.txt';
  if(not SetFileAttributes(PChar(filename), FILE_ATTRIBUTE_NORMAL)) then
  begin
    showmessage('file attribute to normal error !');
  end;
  i:=0;
  bDelete:=DeleteFile(filename);
  //刪5次試試
  while((i<5) and (not bDelete)) do
  begin
    Sleep(1000);
    bDelete:=DeleteFile(PChar(filename));
    Inc(i);
  end;
end;