Код:
procedure TForm1.ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
begin
with (Sender as TListBox) do
Items.Move(ItemIndex,ItemAtPos(Point(x,y),True));
end;
procedure TForm1.ListBox1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin
Accept := (Sender=Source);
end;
Не забудьте в ListBox присвоить свойству DragMode значение dmAutomatic.