procedure SelectAll(DBGrid: TDBGrid);
var
  tmp: TBookMark;
begin
  with DBGrid.DataSource.DataSet do
  begin
    tmp := GetBookmark;
    DisableControls;
    First;
    While not Eof do
    begin
      DBGrid.SelectedRows.CurrentRowSelected := true;
      Next;
    end;
    EnableControls;
    GotoBookmark(tmp);
  end;
end;